Question 762837
{{{x}}}= number of correct answers.
Then,
{{{20-x}}}= number of incorrect answers, and
{{{score=5x-2(20-x)}}}
So, if Phillips score was 72, for him,
{{{5x-2(20-x)=72}}}
That's the equation we have to solve.
{{{5x-2(20-x)=72}}} --> {{{5x-40+2x=72}}} --> {{{7x-40=72}}} --> {{{7x=72+40}}} --> {{{7x=112}}} --> {{{x=112/7}}} --> {{{highlight(x=16)}}}