Cuz she divided 23 and 8 and got 21 then she added 3+3= 6 + 4= 10
I you're looking for the equation, it is

and If you need me to solve it, it is
I think it's 25 in. squared
Answer:
Slope = 46.000/2.000 = 23.000
x-intercept = 6/23 = 0.26087
y-intercept = -6/1 = -6.00000