F(1) = 120, f(n)= Fin-1) +
n
for

First, convert 54 into a fraction. 
It would be 54/1.

Now multiply 7/9 and 54/1 across; multiply the numerator by the numerator and the denominator by the denominator.

7 x 54 = 378
9 x 1 = 9

We get 378/9.

9 can go into 378 exactly 42 times.

So, 7/9 x 54 = 42.