0.5 x 1/10 = 0.05 All you do is multiply
The student wrote the wrong operation. "The sum of 5y and 3" translates to 5y+3. And here means addition.
There is a rule:
One input(x-value) can only have one output(y-value) in order to be a function.
If one input has more than one output, it is not a function.
(This doesn't apply to outputs, one output can have more than one input and still be a function)
The 1st option is not a function because the inputs 9 and 10 have more than one output.
The 2nd option is not a function because the input 3 has more than one output.
The 3rd option is a function because each input only has one output.
The 4th option is not a function because the input 5 has more than one output.
3 + 2 + 1 + 2 = 8, which is the amount of sweaters.
The probability of a brown sweater is 2 / 8 = 0.25
And the probability of a green sweater is 1 / 8 = 0.125.
Multiply the two probabilities together to get the probability of choosing brown then green:
0.25 * 0.125 = 0.03125.
To convert a decimal to fraction, you multiply the numerator and denominator, or in this case

by 1000 which gets

Which can be simplified to:

.
Hope this helps.
First factor each number
39=3*13
52=4*13
Now find the greatest common factor, which in our case is 13.
Answer: 13