Question 591449
a = the first number
b = the second number

b = 2*a + 4
a + b = 13

a + (2*a + 4) = 13
a + 2*a + 4 = 13
3*a + 4 = 13
3*a + 4 - 4 = 13 - 4
3*a = 9
3*a/3 = 9/3
a = 3
b = 2*3 + 4
b = 6 + 4 = 10

a + b = 3 + 10 = 13

The two numbers are 3 and 10.