book Maths Puzzle Numerical Ability

I need to simplify this:

10X+4+X-9

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book Other Question

Use this problem for #3 and 4.
Lucy rides her bike 4 km/h faster than Kim.
Lucy travels east for 2 hours.
Kim travels west for 2 hours.
They are then 80 km apart.
How many km/h is Kim traveling?
To: xcentaur(44)
e.g. Find the solution set.
x^2+ y^2 = 8, and 16x + 4y^2 = 80