make the dissimilar fractions similar
get the lcd of the denominators
4= 4, 8, 12...
12= 12, 24, 36...
the lcd of 4 and 12 is 12
1/4 = ?/12
5/12 = ?/12
divide your lcd with the current denominator( in this case 4 and 12)
12÷12=1
12÷4=3
after dividing it you have to multiply it with the current numerator (1 and 5)
3*1= 3
1*5= 5
and these two are now your numerators
1/4 = 3/12
5/12 = 5/12
now you can subtract the fractions
7 3/12 - 2 5/12 = 5 -2/12
