If the first three terms of your sequence are 3/4, 1, 5/4, the first term is obviously 3/4 and the common difference is 1/4. This is an arithmetic sequence.
We can write a general formula for the nth term of this sequence as follows:
a(n) = a(1) + (n-1)(1/4), or, since a(1) = 3/4,
a(n) = 3/4 + (n-1) / 4
Then a(22) = 3/4 + (22-1)/4, or 3/4 + 21/4, or 24/4, or just 6.
