Some more problems I would like checked please. Numbers in red are exponents. My answers are inbold.

Problem 1:(Simplify)

(4a2) (5a)

= 42(a2) * 5(a)

= 4a2 * 5a

= 4 * 5 * a2 * a

= 20a2

________

Problem 2:(Simplify)

(-3xy) (4x2y3)

= -3 (x)(y) * 4 (x2)(y3)

= -3xy * 4x2y3

= -3 * 4 * x * x2 *y * y3

= -12x2y3

__________

Problem 3:(Simplify)

(-3x3y2)(5x5y)

= -3(x3)(y2) * 5(x5)(y)

= -3x3y2 * 5x5y

= -3 * 5 * x3 * x5 * y2 * y

= -15x15y2

__________

Problem 4:(Simplify)

(-3ab2c3)(-5ac)

= -3(a)(b2)(c3) * -5(a)(c)

= -3ab2c3 * -5ac

= -3 * -5 * a * b2 * c3 *c

= 15ab2c3

Thanks!