Solution:
Given:
Let the missing number be represented by y.
Thus,
[tex]\frac{2}{3}\times y=1[/tex]
To solve for y, we have
[tex]\begin{gathered} \frac{2y}{3}=1 \\ cross\text{ multiply,} \\ 2y=3 \\ divide\text{ both sides by the coefficient of y, which is 2} \\ \frac{2y}{2}=\frac{3}{2} \\ \Rightarrow y=\frac{3}{2} \\ \therefore y=1\frac{1}{2} \end{gathered}[/tex]
Hence, the number that must be in the box is
[tex]1\frac{1}{2}[/tex]
The correct option is A
