Question 602805
A student has taken T tests and has a 90 average What score must he get on his next test in order to raise his average to 91 
:
Let x = the score required to raise the average to 91
:
The equation
{{{((90t+x))/((t+1))}}} = 91
:
multiply both sides by (t+1)
90t + x = 91(t+1)
90t + x = 91t + 91
:
Subtract 90t from both sides
x = 91t - 90t + 91
x = t + 91