How do you check?

-5r+-3=51

-5r + (-3) = 51

Add 3 to both sides:

-5r = 54

Divide both sides by - 5 to get r alone:

r = - 10.8

To check this, plug in - 10.8 into the equation: - 5 (-10.8) + (-3) = 51

54 + (-3) = 51

54 - 3 = 51

51 = 51

This statement is true, so the answer is correct.