you need a common denominator in order to add/subtract fractions. for example:
1/4+3/2=?
1/4+6/4=7/4
what i did there was multiply 3/2 by 2/2 to get the denominator to equal 4. the reason it’s 2/2 is cause what you do to the bottom is what you do to the top.
3/2(2/2)= 6/4
