SAT Math / Linear Relationships
Solve any SAT system of two linear equations by combining the equations so one letter cancels, and tell from the coefficients when a system has no solution or infinitely many.
The equations 4x plus 3y equals 18 and 2x minus 3y equals 0 are stacked, and adding them crosses out plus 3y and minus 3y, leaving 6x equals 18, so x equals 3. Then the two equations are graphed as lines that cross at the point 3, 2, the pair that makes both true. Next, for 5x plus 2y equals 21 and 5x minus y equals 9, a gray pointer picks Subtract them, and the 5x terms are crossed out, leaving 3y equals 12. Then, for a shop that sold 30 shirts, some at 8 dollars and some at 15 dollars, for 310 dollars, the pointer clicks the equation 8s plus 15t equals 310, the one that counts dollars. Finally, answer how many solutions the system x plus 2y equals 5 and 3x plus 6y equals 12 has, using the buttons after the picture.
