According to the question we have the following data:
the sum of 12 and x is -7
This problem can be resolved by formulating the following equation:
if the sum of 12 and x is -7 that means that:
Therefore, to calculate x we would have to make the following:
12 + x=-7
x=-7-12
x=-19
If x is -19 then if we substitue this value in the original equation we would find that the result is correct:
the sum of 12 and x is -7
12 +(-19)=-7