Solution:

Given, a÷3=b÷4=c÷5

Let's assume that a=3x, b=4x and c=5x

Substitute these values in the given expression, we get

2a 3b-2c÷4a-b 2c

= 2(3x) 3(4x) - 2(5x) ÷ 4(3x) - 4x (2)(5x)

= 6x - 10x ÷ 12x - 40x

= -4x ÷ -28x

= 1/7

Hence, the value of the given expression is 1/7.

Explanation:

To solve the given expression, we need to substitute the given values of a, b and c in the expression. After that, we can simplify the expression using the basic arithmetic operations.

We have assumed the value of x to be a common factor in a, b, and c. This will help us in simplifying the expression.

Finally, after simplifying the expression, we get the value of the expression as 1/7.

Therefore, the solution to the given expression is 1/7.