Step-by-step explanation: The equation for this is simple.
Take x as the smallest number of the 4 numbers. The second number would be x +2, third number is x+4, and the fourth number is x+6. you add these together, and you get: 4x +12 = 48, you then solve this as a linear equation. 48-12 = 36. Then you divide by 4, which gives you 9 as the smallest number of the 4 numbers. Remember that the second number is 9+2=11, third is 9+4=13, and the fourth is 9+6=15. If you add these together you get 9+11+13+15=48.