2) x = 5

2x + y = 10

3) 5x - 2y = 3

y = 2x

Simple, it's plug n chug.

x=5

2 (5) + y=10

10+y=10

isolate the variable

10+y=10

-10 - 10

y=0

Thus, your x=5 and your y=0. (0,5)

For the Second equation

5x-2 (2) = 3

5x-4=3

then,

5x-4=3

+4 + 4

5x=7

x=1.4

Thus, your x=1.4 and your y=2. (1.4,2)