To find x, we want to isolate our 3 from our x-values. You can add three to both sides of the equation and get it to the other side and then subtract 1/5x from 5x.
(5x - 3) + 3 = ((1/5)x) + 3
5x = (1/5)x + 3
5x = (25/5)x
((25/5)x) - (1/5)x = ((1/5)x + 3) - (1/5)x
(24/5)x = 3
From here, you would want to solve for x. This would mean multiplying 3 by 5 and dividing your product by 24.
4 1/3+7 2/4=4+1/3+7+1/2=11+(1/3+1/2)=11 5/6. For some reason, the fact that the question said 7 2/4 instead of 7 1/2 suggests that you may have misread the problem.