The height of a triangle is 4 m less than its base. the area of the triangle is 48 m².

what is the length of the base?

Let the height be h and base =b
then h=b-4
area= 1/2 x b x h
48= 1/2 x b x (b-4)
48 =1/2 x b^2 - 4b
2 x 48 = b^2 -4b
b^2 - 4b - 96=0
b2 - 12b + 8b - 96 =0
b(b-12) + 8(b-12) = 0
either b= 12 m or b=-8(rejected)
hence, base =12m and height = 8 m

These are the multiples of 15 but what you are probably asking or what are the factors of 15