Answer:
1. X = 17/A  --- answer is (A)
2.  (6, 0.7) (10, 1.9)
3. $10.99D + $9.99  ≤ $100
Step-by-step explanation:
1. AX + 4AX = 51 + 2AX
  5AX = 51 + 2AX .... -2AX both side
3AX = 51   .. divide 3A
X = 17/A  --- answer is (A)
2. 10y = 3x -11
    (2, 0.5):       3*2 -11 = - 5     10y = 10*0.5 = 5    ..... not correct
     (4, 1)            3*4 - 11 = 1       10y = 10*1 = 10 ....... not correct
    (6, 0.7)        3*6 - 11 = 7       10y = 10*0.7 = 7  .....Correct
    (8,2.3)          3*8 -11 = 13       10y = 10*2.3 =23   ..... not correct
    (10, 1.9)        3*10 -11 = 19       10y = 10*1.9 = 19   .... correct
3.  1D cost $10.99
     D piece cost: $10.99D
      Shipping: $9.99
     No more than $100: ≤ 100
D piece DVD + Shipping withtotal no more than $100: 
$10.99D + $9.99  ≤ $100