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**Mush** y = mx + C

m is the gradient, which is -5.

y = -5x+C

You know it passes through the point (3,6)

6 = -5(3) + C

C = 6+15 = 21

therefore y = -5x+21. This is the equation of the line.

A straight line and the coordinate axis in the first quadrant forms a triangle. You need the area of this triangle... So you need to know the length of the base, and the height, since area = 0.5(base)(height).

The base goes from x= 0, to the point where the line cuts the x axis, which happens when y = 0.

y =-5x+21 = 0

Solve for x. And then x is your base.

The height is from y = 0, to where it cuts the y axis, which is when x =0

y = -5(0)+21 = 21

So the height is 21.

You should now be able to find the area.