1. John lost 9 golf balls in the golf course, and when he returned home, he has 14 golf balls. Let the original number = x. Note that lost = subtract.
x - 9 = 14
Isolate the x. Note the equal sign. What you do to one side, you do to the other. Add 9 to both sides
x - 9 (+9) = 14 (+9)
x = 14 + 9
x = 23
John started with 23 golf balls.
----------------------------------------------------------------------------------------------------------------
2. Marsha divided cookies into groups of 12. If she had 6 dozens cookies when she was done, how many cookies did she start with?
Note that dozen = 12
Multiply the amount of groups with 12.
6 x 12 = 72
Marsha started with 72 cookies.
----------------------------------------------------------------------------------------------------------------
hope this helps