(15) see below   (16) 284   (17) option 1   (18) option 3  Â
        (19) see below   (20) 33   (21) L = 50, w = 10
Step-by-step explanation:
15) Â 7xy + 3x + 5
   ↓    ↓    ↓
   ↓    ↓    5 is a term with no variable so is a constant
   ↓    3x is a term with a coefficient of 3
   7xy is a term with a coefficient of 7
     Constant     Coefficient     Term
7 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â X
3x                              X
5 Â Â Â Â Â Â X Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â X
16)  12a²  - 3 |b|  +  2a    ; a = -5,  b = -2
  12(-5)² - 3 |-2| + 2(-5)
 = 12(25)  - 3(2)  - 10
 = 300   - 6    - 10
 =   294     - 10
 = 284
17) 4(k + 5) = -2(9k - 4)
  4k + 20 = -18k + 8        Distributed 4 and -2
  22k + 20 =      8        Added 18k to both sides
  22k     =  -12            Subtracted 20 from both sides  Â
       k = -12/22          Divided 21 from both sides
       k = -6/11           Simplified (GCF = 2)
18) V = π r²h
  V/(π r²) = h         Divided π r² from both sides
         Â
19) v = s² + (1/2)sh
   v - s² = (1/2)sh       Subtracted s² from both sides
  2(v - s²) = sh         Multiplied both sides by 2
  2(v - s²)/s = h         Divided s from both sides
              1     2    3
subtract s²      X
divide by s                  X
multiply by 2 Â Â Â Â Â Â Â Â Â X
20) F = (9/5)C + 32 Â Â ; F = 91
   91 = (9/5)C + 32
   59 = (9/5)C              Subtracted 32 from both sides
  295 = 9C                Multiplied both sides by 5
  32.8 = C                 Divided 9 from both sides
    33 = C                Rounded to the nearest whole number
21) Perimeter (P) = 2Length (L) + 2width (w)
Given: P = 120, Â Â L = 5w
        P = 2L + 2w
      120 = 2(5w) + 2w
      120 = 10w + 2w
      120 = 12w
      10 = w
                L = 5w
                  = 5(10)
                  = 50