【答案解析】When solving systems of equations, the best thing to do first is to isolate one of the variables. In this problem, you can do so by changing the sign on the bottom equation: x-2y=14 -x+4y=8 Add the two equations together (note that the x terms cancel out): 2y=22 y=11 Choose one of the original equations and substitute 11 in for y. Solve for x: x-2(11)=14 x-22=14 x=36 It is a good idea to test your answers by substituting x and y values into both of the original equations.

【答案解析】This problem is a little trickier than the first, as you cannot simply change the sign of one of the equations to isolate one of the variables. In this situation, you have to make the coefficients the same through multiplication. Since you know that 4 and 6 both go into 12, use the x term. Multiply the top equation by 3, and the bottom by 2: 12x-6y=18 -12x+10y=14 Add the two equations together (note that the x terms cancel out): 4y=32 y=8 Finally, choose one of the original equations, substitute 8 for y, and solve for x.

【答案解析】The first step is rearranging the equations to align like terms: 3x-y=18 4x+6y=24 Multiply the top equation by 6 and add the equations:

【答案解析】First, distribute the 8 to get 8y+8x=12. You can then multiply the second equation by -2 to isolate one of the variables, and rearrange the equations to line up the like terms: 8x+8y=12 -8x+6y=44 Add the equations together (note that the x terms cancel out): 14y=56 y=4 Now choose one of the original equations, substitute 4 for y, and solve for x.

【答案解析】Line up the like terms in both equations: 4x-y=63 x+3y=6 Multiply the top equation by 3 and add the equations: 12x-3y=189 x+3y=6 Note that the y terms cancel out: 13x=195 x=15 Now substitute 15 for x in one of the equations. x+3y=6 15+3y=6 3y=-9 y=-3