Answer:
3 years old is Joshua.
Explanation:
Let y represents the age of Grandpa Collins and x represents the age of grandson Joshua.
As per the given statement: Grandpa Collins is 2 years more than 25 times as his grandson Joshua.
"25 times as his grandson Joshua" means 25x
"2 years more than 25 times as his grandson Joshua" means 25x +2
⇒ y = 25x + 2 ......[1]
Also, it is given : Grandpa Collins is 77 years old
⇒ y = 77 years
Substitute y =77 in [1] to solve for x;
77 = 25x + 2
Subtract 2 from both sides of an equation:
77 -2 =25x+2 -2
Simplify:
75 = 25x
Divide both sides by 25, we get;

Simplify:
3 = x
Therefore, the age of Joshua is, 3 years old.