x5−13=7
\boxed{x=100}
Step 1 :x5−13+13=7+13
Step 2 :x5=20
Step 3 :5∗x5=20∗5
Step 4 :x=100
Step 5 :1005−13=7
Step 6 :20−13=7
Step 7 :\boxed{x=100}