Question 716028
Let j=john's age now
Let t=terry's age now


Each person___________4years ago_____________now_____________in 5 years
john__________________{{{j-4}}}________________j_______________{{{j+5=3(t+5)}}}
terry_________________{{{t-4}}}________________t_______________
Further data________{{{(j-4)+(t-4)=20}}}___________________________


The information shown in the table is directly from the problem description.  Two variables as unknowns were assigned and they occur in two equations.  


The system to solve is this one:
{{{j+5=3(t+5)}}}
{{{(j-4)+(t-4)=20}}}
Which should first be simplified to ....


SYSTEM TO SOLVE:
{{{highlight(j-t=-8)}}}
{{{highlight(j+t=28)}}}


Easiest way from there is add both equations to eliminate t.
2j=36
j=18

Use either equation to find t.
t=28-j
t=28-18
t=10


Final Numeric Result: Terry is 10 and John is 18.