adding the 2 equations, we see the X's go away and we are left with: 10y=10. we can simplify and solve for y by dividing both sides by 10 and we are left with y=1
plugging 'y=1' into the fist equation we get: -7x+6=34. we can now solve for x by subtracting 6 from both sides and dividing both side by –7, so we are left with: x=–4
we can check by plugging both x and y into one of the original equations:
Okay so 6.25 a student then it goes to 4.50 for 15 more students at 70 students its 358.75 now it drops another 1.75 so it would be 368.75 for 80 students so the equation is 4.48 x 80 = 368.75. enjoy :D