Question

A textbook store sold a combined total of 427 physics and history textbooks in a week. The number of history textbooks sold was 79 less than the number of physics textbooks sold. how many textbooks if each type were sold?

Answer 1

This is a sum and difference problem.

If you don't like system of equations, you can solve this problem doing the following:

Physics books (larger of the two numbers) = (427+79)/2 = 253

History books (smaller of the two numbers) = (427-79)/2=174

Check:

253+174=427 ✔

253-174=79 ✔

Answer 2

Set the equations. Let h = history textbooks, and p = physics textbooks

p + h = 427

p = h + 79

Plug in "h + 79" for "p"

h + 79 + h = 427

Simplify. Combine like terms

2h + 79 = 427

Isolate the h. Do the opposite of PEMDAS. subtract 79 from both sides.

2h + 79 (-79) = 427 (-79)

2h = 348

Isolate the h. Divide 2 from both sides

2h/2 = 348/2

h = 348/2

h = 174

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Plug in 174 for h in one of the equations.

p = h + 79

p = 174 + 79

p = 253

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Answer:

History Textbooks = 174

Physics Textbooks = 253

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hope this helps