Answer:
12 m
Step-by-step explanation:
The formula for the area of a triangle is ...
A = 1/2bh . . . . . b represents the base; h represents the height
We are told that the height is 5 m less than the base, so we have ...
42 = (1/2)(b)(b -5)
84 = b(b-5) . . . . . . . . multiply by 2
We want two factors of 84 that differ by 5. The factors are ...
84 = 1·84 = 2·42 = 3·28 = 4·21 = 6·14 = 7·12
The relevant factors are 7 and 12, so now we know b-5 = 7 and b = 12.
The length of the base is 12 m.
