Diego's bag contains 9 times as many seashells as Justin's bag. If Diego gives 12 seashells to Justin, the two boys will have the same number of seashells. What is the total number of seashells?
d = 9j
d-12 = j + 12 sub in the red equation
9j -12 = j + 12
8j = 24
j = 3 so j had 3 to start with...then gets 12 and has 15 ....they BOTH now have 15 for a sum total of 30 shells