Question 681487
Setup Equation using T and total number of problems and (.66 comes converting % to decimal) 66% divide by 100)
{{{(T-7)/T = .66}}}
Multiply both sides by T
{{{T-7=.66T}}}
Add 7 to both sides and subtract .66T from both sides
{{{.34T=7}}}
divide both sides by .34
T=20.588
Round Answer 
21
Total number of problems on test is 21.