Elevating the averages

the average of 5 numbers is 5.so,their sum total is= $5 \times 5=25$

the average of 7 numbers is 7.so,their sum total is= $7 \times 7=49$

so, $x+y=49-25=24$

and ,their average is= $\frac{24}{2}=12$

If the average of 5 numbers is 5, their sum must be 25. If the average of 7 numbers is 7, their sum must be 49. This means the sum of the two new numbers is $49 - 25 = 24$ , and their average must be $\boxed{12}$ .