เฉลยแบบฝึกหัด

1 2X+5=20
 วิธีทำ 2X+5=20
                2X=20-5
                2X=15
                 X=15/2
                 X=7.5
2.4D-15=35
วิธีทำ       4D-25=35
                      4D=35+25
                      4D=60
                        D=60/4
                        D=15
3.5+3D=24
วิธีทำ        5+3D=24
                     3D=24-5
                       D=19/3
                       D=6.33
4. -2+3A=20
วิธีทำ         -2+3A=20
                        3A=20+2
                          A=22/3
                          A=7.33
5. 15-2X=25
วิธีทำ        15-2X=25
                     -2X=25-15
                     -2X=10
                      -10=2X
                     -10/2=X
                        -5=X