Given:
Mass of the planet (M) = 5 times the mass of Earth (Me)
Radius of the planet (R) = 9 times the radius of Earth (Re)

To find:
Acceleration due to gravity on the planet (g)

Formula:
The acceleration due to gravity (g) is given by the formula:
g = G * (M / R^2)

Where:
G is the universal gravitational constant, which is approximately equal to 6.67 x 10^-11 N m^2 / kg^2.

Solution:

Step 1: Calculate the mass of the planet (M).
Since the mass of the planet is 5 times the mass of Earth, we can write:
M = 5 * Me

Step 2: Calculate the radius of the planet (R).
Since the radius of the planet is 9 times the radius of Earth, we can write:
R = 9 * Re

Step 3: Substitute the values of M and R into the formula for acceleration due to gravity (g) and calculate the value of g.
g = G * (M / R^2)

Substituting the values of M and R:
g = G * (5 * Me) / (9 * Re)^2

Step 4: Simplify the expression and calculate the value of g.
g = G * (5 * Me) / (81 * Re^2)

Since G, Me, and Re are known constants, we can calculate their values and substitute them into the equation to find the value of g.

Step 5: Substitute the values of G, Me, and Re into the equation and calculate the value of g.
g = (6.67 x 10^-11 N m^2 / kg^2) * (5 * 5.98 x 10^24 kg) / (81 * (6.37 x 10^6 m)^2)

Simplifying the expression:
g ≈ 49.2 m/s^2

Therefore, the acceleration due to gravity on the planet is approximately 49.2 m/s^2.