Question

Describe whether the equation y-3x=7 is a function

Answer 1

y - 3x = 7

can be written as

y = 3x + 7

For every value of x there is a unique value of y.  For example when x = 0 y = 3(0) + 7 = 7

Yes it is a function.

In particular it is a one-to-one function.