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A baby, a mother, and a dog

Question

How much does the baby weigh if the mother weighs 100 pounds more than the combined weight of the baby and the dog, and the dog weighs 60 percent less than the baby?

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25 lbs

nice work! Please elaborate on your answer.

Basic system of equations with 3 variables...from the statements:

Let b = baby's weight, d = dog's weight, w = woman's weight...

if the mother weighs 100 pounds more than the combined weight of the baby and the dog

EQUATION 1: b + d + 100 = w

the dog weighs 60 percent less than the baby

EQUATION 2: d = 0.4*b

and then from the picture, we know

EQUATION 3: b + d + w = 170

Then just solve the system

Substitute equation 2 into equations 1 and 3:

1) b + 0.4b + 100 = w and 3) b + 0.4b + w = 170

1) 1.4b + 100 = w and 3) 1.4b + w = 170

Then substitute equation 1 into equation 3:

1.4b + 1.4b + 100 = 170

Solve for b:

2.8b = 70

b = 25

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