Question 899751
RT=P for rate of pay, time in hours, pay in dollars


Let r = pay rate up to 20 hours
Let u = payrate of any time amount after 20 hours


Teresa's first week:
20 hours of regular time, and 4 hours overtime time.
{{{r*20+u*4=166}}}
{{{20r+4u=166}}}
{{{10r+2u=83}}}


Her second week:
20 hours regular time and 7.5 hours overtime.
{{{20r+(7.5)u=200}}}
{{{40r+15u=400}}}, which although now has no fractions, still should be simplified further;
{{{8r+3u=80}}}


That forms a system of linear equations:
{{{highlight_green(system(10r+2u=83,8r+3u=80))}}}


Choose the method you like.  A good way could be, multiply first equation by 3 and second equation by 2; and eliminate u to first solve for r.
Solving from here is undone for your efforts.