Instruction:
Write an equation to model each scenario. Then use the equation to solve the problem.
Question:
'A population of insects doubles every month. If there are 100 insects to start with, how many will there be after 7 months?'
Answer:
\begin{align} y &= 100(2)^7\\ y &= 200^7\\ y &= \text{Quadrillion insects (WHICH DOESN'T MAKE SENSE)} \end{align}
That just hits me as odd to get $12,800,000,000,000,000$.
Can someone explain to me what I'm doing wrong?
$100(2^7)$ would be a better way to write it. What you have is slightly ambiguous to a new or inexperienced student of mathematics.
Just remember that $xy^z\neq(xy)^z$. Apply the exponent first because of order of operations.