Work Step by Step
In order to solve this algebraic expression, we must isolate the variable. A variable is the letter in the problem (for instance, in the equation 2x=10, x is the variable). The section header tells us to solve the equation using “multiplication or division,” so we know that the only things we should do to solve this problem are multiplication and division. Because multiplication and division are inverse operations (they cancel each other out), we know we must divide when a number is being multiplied by the variable and multiply when the variable is being divided by a number. In the equation $7r=-7/2$, we must get rid of the 7, which is being multiplied by the variable, r, in order to solve. Thus, we divide both sides by 7 to find that r=-.5. (Recall, dividing by 7 is the same as multiplying by 1/7. -7/2 multiplied by 1/7 equals -7/14, which reduces to -½, or, as a decimal, -.5). Therefore, $r=-.5$. When we plug -.5 in for r in the equation, we get that $-7/2=-7/2$, so this answer is correct.