Use the formula to define a linear function whose graph is parallel to the line y = 3x + 5

Use the formula to define a linear function whose graph is parallel to the line y = 3x + 5 and passes through the origin.

Let us have the function y = 3x + 5. This is a linear function.
Let us write down the general form of the equation of a linear function passing through any point of the plane. We get:
y = ax + b, where a, b are any numbers.
Since our function must be parallel to the straight line y = 3x + 5, we have that the coefficients of x and y in the two equations must be proportional.
Then 1/1 = 3 / a.
Hence a = 3.
Since our function must go through the origin (through point (0; 0)), this point must belong to the function.
y = 3x + b.
Substitute (0; 0).
Then we have:
0 = 3 * 0 + c. Hence, at = 0.
Then the equation of our function has the form: y = 3x.