Question

b how much cardboard does it take to make the box: 426 sq. units (2×5×12)+(2×9×12)+(2×5×9)

Explanation:

Step1: Calculate area of first - type face

The formula for the area of a rectangle is $A = l\times w$. For the face with dimensions $5$ and $12$, the area of two such faces is $2\times5\times12=120$.

Step2: Calculate area of second - type face

For the face with dimensions $9$ and $12$, the area of two such faces is $2\times9\times12 = 216$.

Step3: Calculate area of third - type face

For the face with dimensions $5$ and $9$, the area of two such faces is $2\times5\times9=90$.

Step4: Sum up the areas

Add the areas of all three - types of faces: $120 + 216+90=426$.

Answer:

426 sq. units