#### Answer

$y=-4$

#### 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). 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 $-7y=28$, we must get rid of the -7, which the variable is being multiplied by, in order to solve. Thus, we divide both sides by -7 to find that $y=-4$. We plug -4 in for y and confirm that our answer is, indeed, correct.