Question 25494
LEt the working hours in the libaray be x
Let the workign hours of mowing a lawn be y
Now total hours was 25.
So x+y=25
y=25-x (subsistution)
Total money was $164
SO 4x+8y=164
Subsitute for y
4x+8(25-x)=164
4x-8x+200=164
-4x=-36
x=9
y=25-9
y=16


Hence he worked for 9 hours at the libabary, and about 16 hours for mowing the lawn.
Paul.