We let the width be x, this would make the length x+8 so:
Area = length * width
105 = (x+8)x
105 = x²+8x
0 = x²+8x-105
We look for two numbers with a product of 105 and an absolute difference of 8.
105 - 1 = 104 X
35 - 3 = 32 X
21 - 5 = 16 X
15 - 7 = 8 √
Therefore:
0 = (x+15)(x-7)
So the possible value of x are -15 and 7. We cannot have a negative value since a length is never negative.
So the width is 7m and the length is 15m.