Photo has the answer! hope it helped
Psi stands for pounds per square-inch.
It is a measure of pressure, and is the equivalent pressure of putting one pound on a square-inch of area.
For example, someone weighing 180 pounds standing on his feet, with a footprint area of 72 square-inches would exert a pressure of 180 pounds/72 square inches = 2.5 pounds per square-inch, or 2.5 psi.
The goal of all algebra equations is to isolate the variable. In 3 step you should first make sure both variables are on the same side. To do that make sure you use the inverse.
For example:
6a + 9 = 3a + 15
because 3a is positive you're going to want to subtract it.
6a + 6 = 3a + 15
-3a -3a
_______________
3a + 6 = 15
Now it's a 2 step equation and you solve it on from there.
