A rectangle is 15cm x 12cm. If the length is reduced by R cm and its width is increased by R cm. Its area is reduced by 4cm^2.

Answer 1

I assume you are looking for the value of R
Original rectangle has area 15x12 or 180 cm^2

new length = 15-R
new width = 12+R

so 180 - (15-R)(12+R) = 4

solve for R