Ok so we'll go ahead and solve for y first - we just need to get it alone on one side of the equal sign
Step 1: subtract 2x from each side
2x - 7y - 2x = 19 - 2x
This cancels out the 2x on the left, giving us
-7y = 19 - 2x
Step 2: divide both sides by -7
=
+ 
This gives us
y = -19/7 + 2x/7
That should be your answer for the first question. Now solving the next parts are easy. All you need to do is plug in x.
When x = -3
y = -19/7 + 2x/7
y = -19/7 + 2(-3)/7
y = -19/7 - 6/7
y = -25/7
When x = 0
y = -19/7 + 2x/7
y = -19/7 + 2(0)/7
y = -19/7
When x = 3
y = -19/7 + 2x/7
y = -19/7 + 2(3)/7
y = -19/7 + 6/7
y = -13/7
Hope that helps! Feel free to ask if I can help with anything else :)
For 5-3/12 the equivalent expression is 60/12-3/12 And then for 1-4/9 the equivalent expression 9/9-4/9
Let the length of unknown side be x
So, hypotenuse = 2x + 1
By pythagorean theorem ie , a² = b² + c²
(2x + 1)² = x² + 15²
4x² + 1 + 4x = x² + 225
3x² + 4x -224
(3x +28)(x-8)
x = -9.33 , 8
Since, length can't be negative
x = 8
∴Unknown side length = 8 m
Length of hypotenuse = 2 x 8 + 1 = 17 m
Hope it helps now.
The answer to your problem is 50b+8