Hi Pricila L.
19, 20, and 21
You have 3 consective numbers
x
x+1
x+2
Their sum is equal to 18 more than twice the largest number
18 + 2(x+2)
Therefore
x + x +1 + x + 2 = 18 + 2(x + 2)
Combine like terms
3x + 3 = 18 + 2x + 4
3x + 3 = 22 + 2x
Isolate the variables and constant on opposite sides of the equal sign by
Subtractig 2x from both sides of the equation and subtracting 3 from both sides of the equation
3x - 2x = 22 - 3
x = 19
Make the substitutions in the original equations
x+1 = 20
x+2= 21
18 +2(x+2) = 18 + 2(21) = 18 + 42
Repeat with the numbers
19 + 20 + 21 = 18 + 42
60 = 60
Hope this helps