We have the following triangle:
the area of this triangle is the following:
[tex]\begin{gathered} A=\frac{b\cdot h}{2} \\ \Rightarrow A=\frac{3.5\cdot7}{2}=\frac{24.5}{2}=12.25 \\ A=12.25\operatorname{cm}^2 \end{gathered}[/tex]
Since Senora Cruz sill use four triangles on the door decoration, we have that the area of the original triangle will be multiplied by 4:
[tex]4\cdot A=4\cdot12.25=49\operatorname{cm}^2[/tex]
Thus, senora Cruz will use 49 square centimeters for the triangles
