Math Teacher Gaskin

 6) 6x + 42 = 126 subtract 42 from both sides
      - 42 = -42
6x          = 84   divide both sides by 6
x            =14    Check: 6(14) + 42 = 126, 84 + 43 = 126 CHECK

7) 31 = 11A-24 add 24 to both sides
+24    = +24
 55      = 11A divide both sides by 11
   5      = A     Check: 31 = 11(5) -24? 31=55-24 CHECKS

8) -20y-2 = 8 Add 2 to both sides
           +2 = +2
-20y         = 10  divide both sides by -20
     y          = 10/-20 = -.5   CHECK -20(-.5)-2 =8 ? 10-2 = 8 CHECKS

9) 18 = 16+ 5B subtract 16 from both sides
    -16 = -16
        2 = 5B divide both sides by 5
2/5       = B CHECK: 18 = 16 + 5(2/5) ? 18 = 16 + 2 CHECKS

10) 7 + (3/5) d = -5 Subtract 7 from both sides
(3/5)d = -12 multipy both sides by (5/3)
d = -12(5/3) = -60/3 = -20 CHECK 7+(3/5)(-20)=-5? 7 -(60/5)=7-12 = -5 CHECKS

11)
2.4n -2.4 =    2.4 Add 2.4 to both sides
        +2.4 = +2.4
2.4n          =   4.8 divide both sides by 2.4
     n          =      2   CHECK: 2.4(2)-2.4 = 2.4? 4.8-2.4 = 2.4 CHECKS

12)
1.06P + 3.25 = 22.86 Subtract 3.25 from both sides
           - 3.25 =  -3.25
1.06P            =  19.51 divide both sides by 1.06
       P = 19.51/1.06=   18.40566037736
CHECK: 1.06* 18.40566037736 + 3.25 = 22.86?            CHECKS

13)
200 =   4 -(7/2)m Subtract 4 from both sides
  -4  = -4
196 = -(7/2) m    MULTIPLY BOTH SIDES BY -(2/7)
196*(-2/7) = m  NOTE 196/7 = 28
28*(-2) = m = -56 CHECK 200 = 4-(7/2)*(-56) = 4-(-196) CHECKS