Y=2x or y=x+2 If you plug in the ordered pairs for both, they fit.
The second survey is more believable because there is randomness in the second rather than the first survey. Since the second company surveyed in all interest levels while the first company only surveyed their best customers. Random sampling like what the second company did helps produce representative samples by removing voluntary response bias and undercover age bias.
Consider the function

, which has derivative

.
The linear approximation of

for some value

within a neighborhood of

is given by

Let

. Then

can be estimated to be

![\sqrt[3]{63.97}\approx4-\dfrac{0.03}{48}=3.999375](https://tex.z-dn.net/?f=%5Csqrt%5B3%5D%7B63.97%7D%5Capprox4-%5Cdfrac%7B0.03%7D%7B48%7D%3D3.999375)
Since

for

, it follows that

must be strictly increasing over that part of its domain, which means the linear approximation lies strictly above the function

. This means the estimated value is an overestimation.
Indeed, the actual value is closer to the number 3.999374902...