Let
y-------> number of books read during the month [tex] 1 [/tex]
x------> number of picture of a book
we know that
[tex] y=2x [/tex]
in this problem
for [tex] x=3\ pictures [/tex]
calculate y
[tex] y=2*3=6\ books [/tex]
therefore
the answer is
The number of books read during the month [tex] 1 [/tex] is [tex] 6\ books [/tex]