Algebra 2

In the second sentence, it says this:
"In 10 years, twice John's age decreased by Mary's age is 35."
Choice 1 doesn't solve the problem because Mary is also 10 years older by then.

For that choice to be correct, the system of equations would have to look like this.
y = x + 5 and y + 10 = 2 (x + 10)

Good work Bliu1. I think that I have interpreted the words just a little differently from you,

John is 5 years older than Mary. This is the first equation on all 3 choices.

In 10 years, twice John's age decreased by Mary's age is 35,
In 10 years John will be (y+10) years and Mary will be (x+10) years so
2(y+10) - (x+10) = 35

and John's age (in 10 years time) will be twice Mary's current age. [ i take current age to mean her age today, not her age in 10 years time]
What does this sentence tell you?

Maybe there is more than 1 correct answer.
Find their ages now.
If x is Mary's age now and y is John's age now, which system of equations could not be used to solve the problem?

1. y = x + 5 and y + 10 = 2x
2. y = x + 5 and 2(y + 10)-(x + 10) = 35
3. y = x + 5 and 2(y + 10) = x