Answer:
Jack's gross pay was $2625
Step-by-step explanation:
Jack pays 20% tax on his gross pay.
After tax, Jack's pay was $2100.
This means "20% subtracted from WHICH NUMBER (gross pay) will give us 2100?"
We can translate this statement into an equation (letting gross pay be [tex]x[/tex]):
[tex]x-(0.2)(x)=2100\\0.8x=2100\\x=\frac{2100}{0.8}\\x=2625[/tex]
Hence, Jack's gross pay was $2625.