The way to convert mixed fractions into improper fractions is to multiply the whole number by the denominator, and then add that product to the numerator. After you get the final number, that will be the new numerator and the denominator will stay the same.
So in this case, we multiply 7 with 4 and then add 1:
7*4 = 28 28 + 1 = 29
And the improper fraction of 7 1/4 is 29/4
Do the same with 2 4/5. Multiply 2 with 5 and add 4 like this:
To get the simple interest, we must use the formula: I= (p)(r )( t) So, in this one we need to multiply $900x18x9.% and the answer will be $128.25. This is the amount of interest they are going to pay per year.