First we'll find the Interest no. 1, which is simple interest, assuming the time 1 year:
S.I= PRT/100
S.I= 780*5.2*1/100
S.I=$40.56
Now we'll find interest no.2, which is compound interest, time is 6 years, Principal amount (780) will remain the same as well as the rate thus (putting in the formula of compound interest- annual- ):
H=number of hours m=total salary m=15.50h+50 put 400 in for m 400=15.50h+50 now solve for h 400=15.50h+50 -50. -50 350=15.50h Divide 350 by 15.50to get your final answer you get a long decimal so I rounded it. 22.6 hours