I teach the upper grades in my school, yet I continue to see kids who do not even have basic algebra skills in place. As a parent, I'm very aware of what my own children are learning in school. For the most part, I've been happy with their progress, but as they rise in grade level, I'm starting to see more emphasis on a loose understanding of the concepts and less emphasis on skills__particularly skills with arithmetic of fractions. The main problem with what I see with my students and my own children is that kids are taught "concepts" and are not taught skills__unless they're lucky enough to have a teacher who knows better. Most particularly, children are not taught mastery of arithmetic with fractions. Unfortunately, virtually all of their future math education depends on being able to do fractional arithmetic.
Graphing Linear Equations. If you have several sets of x and y coordinates, you can now draw lines on a graph. Free math worksheets can drill you on plotting x and y coordinates while graphing linear equation. A linear equation when drawn on a line graph always yields a straight line. Take "y = 2x + 1" for example _ a linear equation. Assign any three numbers to x, and then solve for y. Whatever numbers you assign to x and whatever y comes out to be, you will end up with a straight line. Remember to practice on easier math worksheets first before moving on to writing a linear equation or to the systems of linear equations. Good luck!