Question 150416
Find the average x.
{{{x[ave]=(5+8+6+10+12+9)/6}}}
{{{x[ave]=8.33}}}
Find the average y.
{{{y[ave]=(18+15+20+25+25+30)/6}}}
{{{y[ave]=22.167}}}
For a simple linear regression {{{Y=a+bX}}}, use the following formula to find the slope, 
{{{b=(sum( (x-x[ave])(y-y[ave]) ))/(sum((x-x[ave])^2))}}}

{{{b=66.666/33.333}}}
{{{b=2}}}
{{{a=y[ave]-bx[ave]}}}
{{{a=22.167-2(8.333)}}}
{{{a=22.167-2(8.333)}}}
{{{a=5.5}}}
{{{drawing( 300, 300,-5, 25, -5,60,grid( 1 ), 
circle(5,18,.1),
circle(6,15,.1),
circle(8,20,.1),
circle(9,25,.1),
circle(10,25,.1),
circle(12,30,.1),
circle(20,45.5,.3),
blue(line(0,5.5,25,55.5)) )}}}
To estimate for x=20
{{{y(20)=2(20)+5.5=45.5}}}