You must start using a variable which i will use n.
A number increased by 4, n+4, is the the same, =, as 19 minus 2 times the number, 19-2n.
You must then set up the equation using the description n+4=19-2n.
Then solve the equation
3n+4=19
3n=15
n=5
The answer would then be 5.
