How to solve a system of equations by substitution?

If a • b*2 = 1.8 x 10*-7, and c•b/d = 7.2 x 10*-4, find the value of a•d*2/c*2

Awall map has a scale of 128 miles = 6 inches. the distance between springfield and lakeview is 2 feet on the map. what is the actual distance between springfield and lakeview? 384 miles 512 miles 1.13 miles 42.7 miles

You are remodeling your kitchen. you’ve contacted two tiling companies who gladly told you how long it took their workers to tile of a similar size jim completed half the floor in 8 hours. pete completed half of the other floor in 7 hours. if pete can lay 20 more tiles per hour than jim, at what rate can jim lay tiles