You had $9.28 prior to making the withdrawal
-$20.51 = x - $29.79
x = $9.28
Answer:
7
Step-by-step explanation:
12-7=5
or
5+7=12
By either long or synthetic division, it's easy to show that

The quartic will be exactly divisible by

when the numerator of the remainder term vanishes, or for those values of

such that

I'm not sure how to count the number of solutions (software tells me it should be 80), but hopefully this is a helpful push in the right direction.
=,>,<,<,= convert them each to where they match in their units