lets make x equal the the age of the younger man and y equal the age of the older man.
You are given x+y=76 and you can make the equation 2x+16=y since we are told that the older one is 16 more than twice the age of the younger one. Since we have 2 equations and with the same variable and one has y already written in terms of x (y=2x+16) i will use substitution and make the given equaton all in terms of x.
x+(2x+16)=76 (solve this for x)
3x+16=76
3x=60
x=20
Then you can solve for y using the equation the equaion x+y=76 since we now know x=20.
20+y=76
y=56
Second equation is y=2x+16 (can also be written as y-2x=16)
x=20
y=56
I hope this helps. If anything is unclear or you just want further explanation please let me know in the comments.