1) Considering the slope-intercept formula y=mx+b, the slope m=-10 and point (10,120) Let's plug the point and the slope to find the linear coefficient "b" so that we can write the full equation.
(x,y)
(10,120)
m=-10
y=mx+b
120=-10(10)+b
120=-100+b
120+100=b
220=b
2) Writing all these pieces of information, we have :
y=-10x+220
As the equation of that line.