let small notebook = s, large notebook = b
Set the system of equations:
54 = 8s + 10b
s + b = 6
First, solve for b. Isolate the s.
s = 6 - b
Plug in 6 - b for s
54 = 8(6 - b) + 10b
Distribute 8 to all terms within the parenthesis
54 = 48 - 8b + 10b
Simplify
54 = 48 + 2b
Isolate the b. Note the equal sign. What you do to one side, you do to the other. Subtract 48 from both sides
54 (-48) = 48 (-48) + 2b
6 = 2b
Divide
6/2 = 2b/2
b = 6/2
b = 3
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Plug in b for 3 in one of the equations.
s + b = 6
s + 3 = 6
Isolate the s. Subtract 3 from both sides
s + 3 (-3) = 6 (-3)
s = 6 - 3
s = 3
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small notebook = 3, large notebook = 3
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hope this helps