Find the transmission parameter A the circuit
If you reflect the secondary load (2 + 5 ohms) back into the primary it becomes 7/4. The current in the primary of the transformer is V1/(2 + 7/4) = V1/3.75. The current in the secondary is 1/2 of that or V1/7.5.  V2 is just 5 times the secondary current or 5V1/7.5. If A = V1/V2, then A = 7.5/5 = 1.5. So you are correct and your book is in error.