Question

8z-13=7 what's the number that replaces z

Answer 1

8z-13=7 (first, add 13 to both sides)
8z=20
z=20/8
=10/4
=5/2
=2.5

Answer 2

All you do is solve for z. So 8z-13=7. To solve for a variable you have to do the opposite to cancel out the numbers on each side. First you add 13 over to 7 to cancel out 13 on the z side. So 8z=20 is what you have left. Then you divide 8 on both sides to cancel out 8 on the z side. what you are left with is z=2.5. Lastly you plug and check. 8(2.5) - 13 = 7, 20-13=7. And thats correct so z is 2.5.