Question 87818
60-89(60-89x)/2 
The sum has to be 

60 = 89(60-89x)/2

60*2 = 89(60-89x)/2*2

120 = 89*60 - 89*89x

120 = 5340 - 7921x

120+7921x = 5340-7921x+7921x

7921x+120-120 = 5340 -120

7921x = 5220

7921x/7921 = 5220/7921

x = 5220/7921

x = 0.659