**Equilibrium in Consumer Theory:**

In consumer theory, equilibrium refers to a situation where a consumer maximizes their satisfaction or utility given their budget constraint and the prices of goods. This occurs when the consumer allocates their budget in a way that the marginal utility per unit of money spent is equal for all goods consumed.

**Marginal Utility (MU):**

Marginal utility measures the additional satisfaction a consumer receives from consuming one additional unit of a good. It is the change in total utility divided by the change in quantity.

MUx = ΔTUx / ΔQx

Where MUx is the marginal utility of good x, ΔTUx is the change in total utility from consuming an additional unit of good x, and ΔQx is the change in quantity of good x.

Similarly, MUy represents the marginal utility of good y.

**Price and Marginal Utility:**

To determine the marginal utility of good y (MUy) when the consumer is in equilibrium, we need to consider the relationship between price and marginal utility.

According to the Law of Demand, as the price of a good decreases, the quantity demanded increases. This implies that the marginal utility of a good decreases as the quantity consumed increases.

In this case, the price of good x is 10/- and the marginal utility of good x (MUx) is given as 60. This means that the consumer is willing to pay up to 10/- for an additional unit of good x, and the satisfaction gained from consuming the last unit of good x was 60.

**Determining MUy:**

To determine MUy, we can use the concept of the marginal rate of substitution (MRS). The MRS measures the rate at which a consumer is willing to substitute one good for another while maintaining the same level of satisfaction.

The MRS is calculated as the ratio of the marginal utilities of the two goods:

MRS = MUx / MUy

In equilibrium, the consumer allocates their budget in a way that the MRS is equal to the price ratio of the goods:

MRS = Px / Py

Where Px is the price of good x and Py is the price of good y.

In this case, the price of good x (Px) is 10/- and the price of good y (Py) is 20/-. Therefore:

MRS = 10/- / 20/- = 1/2

Since MUx is given as 60, we can substitute this value into the MRS equation:

60 / MUy = 1/2

Solving for MUy:

MUy = 60 * 2 = 120

Therefore, the marginal utility of good y (MUy) is 120 when the consumer is in equilibrium.

**Conclusion:**

In conclusion, when the price of good x is 10/- and the marginal utility of good x is 60, the marginal utility of good y is 120. This is determined by the equilibrium condition where the marginal rate of substitution (MRS) is equal to the price ratio of the goods.

Answer:120
explanation:two goods x and y are said to be in equilibrium when mux/muy=px/py

thus here
60/x=20/40
then x= 120