Which explanation best describes how to solve this problem?
a pet store started the week with a number of frogs to sell. it sold 24 frogs. then, in the middle of the week, the store got a delivery of 19 more. it sold another 11. now the store has 15 frogs left. how many frogs did the store have at the beginning of the week?

a.
guess and test. guess that the store had 45 frogs to begin with. subtract the first number it sold and add the number of frogs delivered to the store (19). then subtract the second amount sold. this gives 29. that is 14 more than 15. add 14 to your guess. the store had 59 frogs to begin with.

b.
draw a diagram. draw 24 dots to represent the first number of frogs sold. add another 19 dots and then add another 11. cross out 15 dots to represent number of frogs left. the 39 remaining dots is the number of frogs at the beginning of the week.

c.
translate into an equation.

15 + 24 – 19 + 11 = b

the store had 31 frogs at the beginning of the week.

d.
work backward. start with the number of frogs the store has left (15). add the frogs that were sold (24 + 11). then add the frogs that were delivered mid-week (19).

the pet store had 69 frogs at the start of the week.