Mrs. Lacson sold a total of 20 + 15 = 35 sweet potatoes. Hence, there are still 80 - 35 = 45 sweet potatoes left unsold.
The answer: 45
Reverse engineering the question: Mrs. Lacson harvested 80 sweet potatoes. She sold 20 of them to Mrs. Adams and 15 of them to Mr. Lenon. How many sweet potatoes are not yet sold?

30 x 1 / 5 = 6 students like Math. 30 x 1 / 3 = 10 students like English. So, 6 + 10 = 16 students like either Math or English. Thus, 30 - 16 = 14 students neither like Math nor English. Since 1 / 7 of the remaining like Science, therefore 14 x 1 / 7 = 2 students like Science. Hence, 14 - 2 = 12 students neither likes the 3 subjects.
The answer: 12
Reverse engineering the question: In a class of 30 students, the teacher polls the students on their favorite subject. 1/5 of the students like Math, and 1/3 like English. 1/7 of the remaining students like Science. The rest don’t have a favorite subject. How many students don’t have a favorite subject?

Camp has 3 * 40 boys = 120 girls. Camp Cedar has a total of 40 boys + 120 girls = 160 children. Camp needs 1 counselor per 8 children, so 160 children / 8 children = 20 counselors needed.
The answer: 20
Reverse engineering the question: Camp Cedar has 40 boys, it has 3 times as many girls. It needs 1 counselor for every 8 children. How many counselors does Camp Cedar need?

Captain America is 1456 / 13 = 112 years old. Peter Parker is 112 / 7 = 16 years old. Ironman is 16 + 32 = 48 years old.
The answer: 48
Reverse engineering the question:
Thor is 13 times older than Captain America. Captain America is 7 times older than Peter Parker, and Ironman is 32 years older than Peter Parker. How old is Ironman if Thor is 1456 years old?