Combining Like Terms -4x - 2 + 5x = -4
I know the answer is -2 but I don’t know how to get -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.

Acomputer store bought a program at a cost of $10 and sold it for $13. find the percent markup

An engineer scale model shows a building that is 3 inches tall. if the scale is 1 inch = 600 feet, how tall is the actual building?