The average height of a 2 year old boy is 38 inches; an 8 year...

Represent the given data as points: $(x1,y1)=$${\displaystyle (2,38)\to 2}$ year old boy is 38 inches year old boy is 38 inches
$(x2,y2)=$${\displaystyle (8,56)\to 8}$ year old boy is 56 inches year old boy is 56 inches
Find the slope ${\displaystyle m=\frac{y2-y1}{x2-x1}=\frac{56-38}{8-2}=\frac{18}{6}=3}$
Use the slope-intercept form of a line: $y=mx+b$
Substitute any point, say (2,38) and $m=3$ to find bb:
$38=3(2)+b$
$38=6+b$
$32=b$
So, the linear equation is: $y=3x+32$
To predict the average height of a 5 year-old boy, substitute $x=5$:
$y=3(5)+32$
$y=15+32$
${\displaystyle y=47\to 47}$ inches

Answer is given below (on video)