a straight line only has 180° at all times so it is a matter of subtraction. 180-68 is 112° so from there you can find #2 as 68°, #3 as 90° and #4 as 90°, and so on.
Expressions cannot <u>be solved. </u>Although they are similar to equations, you can solve an equation, but you cannot solve an expression. You can evaluate it, simplify it, and it can have many variables, however, an expression just exists, it is not a problem that has to be solved.<u> </u>
