Fred is building a model of the bridge shown and he needs to make the triangular support ABC. He has several different pieces of wood at various lengths.
Which of the following three pieces of wood will work for support ABC?
7 in., 9 in., 5 in.
O 6 in., 9 in., 2 in.
O 2 in., 9 in., 7 in.
16 in., 9 in., 7 in.

here's the way that i learned it:

convert them to mixed fractions and then go from there.

3.6 = 36/10 0.5 = 1/2

right now our problem looks like this: 36/10 ÷ 1/2 =

okay, so i learned the method keep it, switch it, flip it.

keep the first fraction in the equation, 36/10

switch the division sign to multiplication ÷ ⇒ ×

switch the numbers on the second fraction  1/2 ⇒ 2/1

okay, so our equation looks like this now:

36/10 x 2/1

okay, so now multiply across. (multiply the top numbers together and the bottom numbers together)

72/10

latly, we need to convert back to a decimal. divide the top number by the bottom one.

to do this, divide the top number by the bottom number

72/10

7.2

i hope this was helpful. this is how i learned dividing with decimals, so it might be kinda complicated. if you still need help, let me know :)