Question 264154
Y=mX+b m=slope
m=2.1 which is positive.
y=2.1x+37
{{{ graph( 300, 200, -20, 5, -10, 50, 2.1x +37) }}} (graph 300x200 pixels, x from -206 to 5, y from -10 to 50, 2.1x +37). 
0=2.1x+37
2.1x=-37
x=-37/2.1
x=17.619 ans for the x intercept.
1990-18=1972 is the year there was no recycling.