amount of interest = $2625
total value of the account = $6125
After the last step, you have to plug x into the equations. 5(5)+8=33 and 8(5)-1=39. You do this because it asks you to find the measurements of the angles, meaning the whole thing, not just x. To check, you add the two values of EFG and EFH, and they should equal EFG. 33+39=72, so it all checks out!
Good luck without a picture
Let X = the number of hours
Plane 1 equals: 850x
Plane 2 equals: 750x
850x + 750x = 4000
1600x = 4000
x = 4000 / 1600
x = 2.5 hours
3 pm + 2.5 hours = 5:30 pm