What word means to find the value of an algebraic expression

If the sales price of a dvd is $20 and the markup is 34%, what is the cost of the dvd?

If a 36 inch yardstick casts a 21 foot shadow, how tall is a building whose shadow is 168 feet? what is the scale factor

Use complete sentences to differentiate between a regular tessellation, and a pure tessellation. be sure to include specific types of polygons in your explanation.