10(x - 5) = -80 i don't understand math that well lol

What is the value of x in the following equation. -x ^3/2 = -27

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8

Agroup of three friends order a combo meal which includes two slices of pizza and a drink each drink is priced at $2.50 the combined total of $31.50 how much is the cost of a slice of pizza