Verified Answer :

21.25 + 1.75 = 23
23 +1.75 = 24.75
24.75 + 1.75 = 26.5
26.5 + 1.75 = 28.25
28.25 + 1.75 = 30
30 + 1.75 = 31.75
31.75 + 1.75 = 33.5
33.5 + 1.75 = 35.25
35.25 + 1.75 = 37
Answer is 9 years

A tree grows 1 3/4 per year.

\(1\frac{3}{4} = \frac{7}{4}\)

Rate of growth =slope(m) =\(\frac{7}{4}\) feet per year

Initial height = \(21\frac{1}{4} = \frac{85}{4}\) feet

Final height = 37 feet

Since there is a constant growth every year , we use linear equation

y= mx+b

Where x is the number of years

b is the initial height and y is the final height

We know the value of m, y and b

Plug in all the values

37 = \(\frac{7}{4}\) x + \(\frac{85}{4}\)

Now we solve for x, subtract the fraction 85/4 on both sides

37 -  \(\frac{85}{4}\) = \(\frac{7}{4}\) x

\(\frac{148-85}{4}\)=\(\frac{7}{4}\) x

\(\frac{63}{4}\)=\(\frac{7}{4}\) x

Multiply both sides by 4/7

\(\frac{63}{4}\)\(\frac{4}{7}\)= x

9 = x

So, it will take 9 years to grow to the height of 37 feet.