Question 253220
This problem could be in word problems geometry or quadratic equations.
Area=L*W
W=L-5
substitute L-5 for W
84=L*(L-5)
84=L^2-5L
L^2-5L-84=0
we ant factors of 84 with a difference of 5
1,84
2,42=6*7=3*2*7
3,14
4,21
6,14
7,12

7 and 12 will do
We want the larger number to be negative
(L-12)(L+7)=0
L=12 since  a rectangle can't have a negative size of 7

W=L-5=7