99 is not divisible by 7, so you take out as much as you can(that's what she said)
If you're quick enough at mental math, you could take out 84 and find you remainder of 5.
But let's say you can't. you would find a multiple of 7 to subtract. Say, 70.
So 99-70= 19. 19-14=5
70÷7=10
14÷7=2
10+2= 12r5