Jonathan saved money to have a party. If he spends 2/8 of his money on food, 1/5 of his money on prizes, and 2/10 of his money on decorations, estimate what fraction of his money he will have left.

You have to make all the fractions have common denominators, so 2/8 is 10/40. 1/5 is 8/40, and 2/10 is 8/40. you add those together and get 36/40. He will only have 4/40 left which simplifies to 1/10. Btw even when you estimate you have to show your work (most of the time)