In this case, you aren't going to get an integer for the value of a, but you can rearrange the equation to equal a.
4a-3=D add 3 to both sides
4a=D+3 divide both sides by 4
a=(D+3)/4 here's your answer
17/2 = 8.5 hours per week
8.5 x 5 = 42.5 hours in 5 weeks
20.21 multiplied by 999.801 is 20,205.97821, so the correct answer would be A. about 20,000
Do the exponents first. 10 to the -4 is 1/10000 or 0.0001 and 10^ -5 is 0.00001. You end up with (1.7*0.0001)(5*0.00001) which is 0.00017*0.00005 which is 0.0000000085 or 0.085*10^-8
