State Ohm's law in words.

Ohm's law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them, provided the temperature and other physical conditions remain constant.

In this configuration, the $2 \, \Omega$ and $5 \, \Omega$ resistors are in series in one branch, and the $3 \, \Omega$ resistor is in a parallel branch. Ammeter $A_1$ measures the current through the $2 \, \Omega$ and $5 \, \Omega$ branch, which is given as $1.5 ,