Sagot :
The number of used books sold will be 7 and that of the new book will be 9.
How to form an equation?
Determine the known quantities and designate the unknown quantity as a variable while trying to set up or construct a linear equation to fit a real-world application.
In other words, an equation is a set of variables that are constrained through a situation or case.
Given
Number of used books = u
Number of new books = v
In the first case;
12u + 4n = 136
In the second case;
28u + 4n = 248
By both equations,
u = 7 and n = 9
So the number of used books is 7 and the new is 9.
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