if y varies directly as x, and y=7 when x=4 find y when x=12

Question

If y varies directly aas x, and y=7 when x=4  find y when x=12

Answer 1

When "y varies directly as x", it means that:

 

y = x + b

 

This is the equation of a straight line with a slope (m) = 1 and a y-intercept of b.  For this problem, use the point-slope form of the straight line equation:

 

y – y₁ = m(x – x₁)

 

In your problem, (x₁, y₁) = (4,7), m = 1, and x = 12.  Solve for y.