The letter "x" is often used in algebra to mean a value that is not yet known. It is called a "variable" or sometimes an "unknown". In x + 2 = 7, x is a variable
To find the surface area, you need to do the following:
A side of the figure is a trapezoid, so you should do 13+5x7 (since there are 2 of the same sides there is no need to divide by two.) and it should equal 126. To find the area of the top of the figure, you need to do 5x2 which equals 10. The area of the bottom of the figure is 26 (13x2), then do 2x3x2 to get the sides on the left and right of the figure. After all of this, add them together. (126+10+26+12=174.)
The surface area should be 174mm.
The US equivalent of "liters to meters" would be something like
"quarts to yards", which is equally meaningless.
Liters and meters don't even measure the same thing. Liters describe
volume, whereas meters describe length or distance. They don't convert
to each other .
If volume units could be converted to length units, then you (or somebody
with a slightly better grasp of his math) would be able to figure out how many
inches of gas he put into his car last week, and the cost of a foot of milk.
