Respuesta :
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
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 ✔