210 books were sold in 3 weeks
Explanation
Step 1
you can easily solve this by using a rule of three
number of weeks=1
sold books=70
then, the rate is
[tex]\text{rate}=\frac{70\text{ books}}{1\text{ we}ek}=70\text{ book}s\text{ per w}eek[/tex]
Step 2
Let
x represents the number of books sold in 3 weeks,then the rate is
[tex]\text{rate}=\frac{x}{3\text{ w}eeks}[/tex]
as the rates are equal
[tex]\begin{gathered} 70=\frac{x}{3} \\ Multiply\text{ both sides by 3} \\ 70\cdot3=\frac{x}{3}\cdot3 \\ x=210 \end{gathered}[/tex]
I hope this helps you
