Answer
Heat transferred would be 189 btu
Work Step by Step
The amount of heat transferred per hour ΔH through a glass window varies jointly with the surface area (A) of the window and the difference in temperature between the areas separated by the glass (ΔT)
That is
$ΔH = k A.ΔT$
Given $ΔH = 135\ Btu$ when $A = 7.5$ square feet and $ΔT = 40\ °F$
=> $135 = k*7.5*40$
=> $k = \frac{9}{20}$
To find $ΔH$ when $A = 12$ and $ΔT = 35$
=> $ΔH = k*12*35 = \frac{9}{20}*12*35 = 189\ btu $
