Question

If y varies directly as x, and y is 48 when x is 6, which expression can be used to find the value of y when x is 2?

Answer 1

the answer for your question is 48/6 ×2

Answer 2

If y varies directly as x,
y = kx


when y = 48, x = 6
plugging this in y = kx

48 = k*6
k = 48/6 = 8.

when x = 2,
y = kx = 8*2 = 16

so I think the expression you're looking for is:
y = 8*2 or y = (48/6)*2.