Let the four numbers be x, a, b, and c, where x is the first number. Average = \frac{x + a + b + c}{4} = 48 ⇒ x + a + b + c = 192. Given, x = \frac{1}{3}(a + b + c). Substitute in the sum: \[x + a + b + c = 192\] \[x + 3x = 192\] ⇒ \[4x = 192\] ⇒ \[x = 48\] Hence, the first number is 48.