Answer:
T' is (-2,5) 
 
Explanation:
To reflect a point across the y-axis, you will note the following: 
1- the sign x-coordinate of the point is flipped while the value remains the same 
2- both the sign and the value of the y-coordinate remain the same 
 
We are given that: 
point T is (2,5) 
Applying the above: 
sign of x-coordinate is flipped and value is the same : 
x- coordinate of T' is -2 
both sign and value of y-coordinate are the same: 
y-coordinate of T' is 5 
 
Based on the above: 
T' would be (-2,5) 
 
Hope this helps :)