[計量] To reproduce an old photograph, ...
To reproduce an old photograph, a phtographer charges x dollars
to make a negative, 3/5x dollars for each of the first 10 prints,
and x/5 dollars for each print in excess of 10 prints. If $45 is
the total charge to make a negative and 20 prints from an old photograph,
what is the value of x?
a. 3
b. 3.5
c. 4
d. 4.5
e. 5
Ans:e
我算法是 10*(3/5x)+(x/5)*(20-10)=45
8x=45 x=45/8
請問我錯在哪?
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