(3/4)x + (5/8) x =4x
.75. .625
.75x +.625x = 4x
1.375x = 4x
subtract 4x from each side because you want to get like terms (x) together.
equation is now
1.375-4x= 0
-2.625x= 0
-2.625× = 0
------------- -----------
-2.625 -2.625
zero can't be divided by anything so
x=0