The interest rate on a second mortgage was 8 3/4%last month. This month the interest rate is 11 1/8%. How many percentage points has the interest rate increased?
Set up an equation.
8 3/4 + x = 11 1/8
Isolate the variable...
x= 11 1/8 - 8 3/4
Find a common denominator (in this case, 8.) You can also, as I'm going to do, convert the mixed numbers into improper fractions.
x= 89/8 - 38/8
Now solve that, convert it back to a mixed number, and there you have it.