Question 936752
Since Jack is 13 years older than Mary, write it like this.
J=M+13, where J is Jack and M is Mary. 
If J+M=153, the substitute J for M+13.
It ends up looking like this- 2M+13=153.---> 2M=140--->M=70
So Mary is 70, and Jack is 70+13=83 years old.
ANSWER: MARY=70,JACK=83