how do you check an answer if

Question

4(j-7)=12
4j-28=12
-16=4j j=4
is this rite?how do you check if rite?

It is wrong. When you add 28 to both sides, one gets
4j= 40

j= 10

in baseball, the pither's mound is 6 in. more than 20 yd from home plate . how many feet is this