One number (a) exceeds another number (b) by 11 so
a = b+11
a + b = 77
Substitute the equation for a into the second equation
(b+11) + b = 77
multiply each side by 1 to remove parentheses
b + 11 + b = 77
Combine like terms
2b + 11 = 77
Isolate the variable
2b = 77-11
Simplify
2b = 66
Divide by 2
b = 33
Now substitute b back into the initial equation for a
a = (33) + 11
a = 44
Check your work by substituting both values into the second equation
44 + 33 = 77
This is true, so 44 and 33 are solutions