Ok. Since the fractions aren't the same, we have to make them common. They both have 30 in common.
4/10 = 12/30 I multiplied this 4 by 3 since I did 10 times 3.
2/3 = 20/30 Same with this one. Since 3 times 10, 2 times 10
Now you add the things to get 32/30, simplify to 1 2/30, and again to get 1 1/15.
Now add
3+2+1/15 = 6 1/15
He used 6 1/15 bags of fertilizer.