Find the product.

(5a+2)³

do you know pascal's triangle or other ways of doing binomial coefficients?

row 3

1 3 3 1

so
(x+y)^3 = 1 x^3 + 3 x^2 y + 3 x y^2 + 1 y^3
here x = 5 a
y = 2
so
125 a^3 + 150 a^2 + 30 a + 8
check my arithmetic