If the perimeter of the rectangle is 10a +12b unit its length is 4a -2b find breadth

a+4b

Explanation:

Since the length is 4a-2b, that means there is 2 of those, since the perimeter is 2l+2w, which basically means 2 values of the length plus 2 values of the width. In this case, the length is 4a-2b so that means we have to subtract twice its value from the perimeter, 10a+12b.

When you do that, you get 2a+8b, which must be divided into 2 because there is supposed to be 2 values of the width. That gets you your final answer, a+4b.