parallel
The two equations are linear.
linear b
Linear A script is a kind of writing system, that Minoan culture used.
horizontal
NONE
You don't really need to know this unless you have any drive, or desire to rise above the dumbified populations and make the world a better place through science. If you do want to do something of value, not just asking people if they want their number 1 super-sized, graphing linear equations is a step in understanding higher level mathematics - the kind of math they used to get folks on the moon, design cars, create amortization schedules, etc.
Acceleration
Of course, equations are going to be studied in arithmetic while in elementary school. A different kind of equations will be studied in algebra and calculus in high school.
Linear
There are several ways to do it - depending, in part, on the kind of equations. Sophisticated methods exist specifically for linear equations, among others. However, for a start, you can combine equations (1) and (2), eliminating one variable; the same for equations (2) and (3), and for equations (3) and (4) (eliminating the same variable in every case). That leaves you with 3 equations with 3 variables. Similarly, reduce the 3 equations in 3 variables, to 2 equations in 2 variables (eliminating the same variable in every case). Combine those into a single equation with 1 variable. Example for eliminating a variable: (Eq. 1) 5a + 3b - 3c + 8d = 28 (Eq. 2) 8a - 3b + 8c - 6d = 8 If you just add up the equations, you eliminate variable b. If you want to eliminate variable a, multiply the first equation by 8, and the second by (-5), then add the resulting equations.
Motion Perpendicular to the ground is called horizontal motion.