Someone is writing the answer so ill just give you this tip for whenever.
A negitive times a negitive is positive
a negative times a positive is negitive
and a positive times a positive is positive (just had to add it to be complete)
Answer:
The first one
Step-by-step explanation:
2x+38=180
2x=142 (or x+x=142 from which 2x=142)
x=71
The unknown angles are each 71
You know this answer is logical as, since two sides are 21 it hints that we are looking at an equilateral triangle, which means two of its angles will be the same
For this case we have that by definition, the volume of a cuboid is given by:

Where:
L: It's the long
A: It is the width
h: It is the height
According to the problem data we have:

So, the volume of the cuboid is:

Finally, the volume of the cuboid is: 
Answer:
