What is the value of 5/z when z=2

Zoe placed colored blocks on a scale in science class. each block weighed 0.8 ounces. the total weight of all the colored blocks was 12.8 ounces. how many blocks did zoe place on the scale? write and solve an equation to find the answer.

The tile along the edge of a triangular community pool needs to be replaced? ?

If x-1 and x+3 are the factors of x3+10x2+ax+b find a and b