To solve the equation m + 4 = 28 what operation do you use

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?

Can someone show me step by step how to do this?

Franklin is purchasing a home for $82,107 and is financing 80% of it. the documentary stamp tax on the deed in his state is $0.70 per $100 or portion thereof. how much will he pay for the documentary stamp tax?