Question

Write an equation whose graph is parallel to the graph of y= 0.5x - 10

Answer 1

0.5 is the gradient. Any equation with a gradient of 0.5 will be parallel to y=0.5x-10.
Any examples: y=0.5x+9. y=0.5x-25.

Answer 2

y = 0.5 x + (any number)

is parallel to the graph of y = 0.5x - 10 .

If the (any number) happens to be -10 , then the two lines
lie right on top of each other, and it looks like there's only
one line on the graph.