See https://web2.0calc.com/questions/please-help_96053.
This is my answer! I solve it by myself, check it out!!!! Sorry for late
Answer:

Step-by-step explanation:
1st you want to find a common denominator. which is 8.
2nd change
to 
3rd you add
and
together an you get 
so what you would do is 20 x 12 and see what you get and the subtract it from 900 and then see what number would take you to 900
Answer:
104.7664068
Step-by-step explanation: