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A textbook store sold a combined total of 228 biology and physics textbooks in a week. The number of blology textbooks sold was three times the number of

physics textbooks sold. How many textbooks of each type were sold?

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User Emmi
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Explanation:

Let us assume p is the number of psychology books and b is the number of biology textbooks.

set up first equation:

we know that the total number of books sold was 393

p+b=393

set up second equation:

we know that there were 79 less biology book sold that psychology so...

p = b + 79

subsitute p in the first equation to solve for b

solve value for p

User Kyle Parsons
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