3/4 is the answer
You first set them equal to each other, the turn 2 1/4 into an improper fraction. So you now have 9/4=3/2+x.
But you can’t just solve yet because the denominators aren’t equal.
So you find the LCM of 2 and 4 which is 4, 2*2=4 and 4*1=4. Don’t forget to also multiply the numerators of the numbers by the number you used to get the LCM.
The Equation should now be 9/4=6/4+x.
Subtract 6/4 on each side.
You’re left with X=3/4