Answer:
The answer to your question is $5.60
Step-by-step explanation:
     1 tulip + 1 daisy + 2 mums = $4.20           (1)
     1 tulip + 2 daisies + 1 mum = $ 3.80         (2)
     2 tulips + 2 mums = $4.80                        (3)
     1 tulip + 3 daisies + 2 mums = ?
tulip = t      daisy = d      mum = m
Process
1.- Find the price of each flower using system of equations
     Solve equation 3 for tulip
      2t = 4.80 - 2 m     divide by 2                            (4)
      t = 2.40 - 1m
2.- Substitute equation 4 in equation 1 and 2
     (2.4 - 1m) + 1 d + 2 m = 4.2
     (2.4 - 1m) + 2d + 1 m = 3.8
3.- Simplify and solve for each flower
      2.4 - 1m + 1d + 2m = 4.2
       1d + 1m = 4.2 - 2.4
       1d + 1m = 1.8                   Equation (5)
      2.4 - 1m + 2d + 1m = 3.8
      2d = 3.8 - 2.4
      2d = 1.4
      d = 1.4/2
      1d = 0.7
4.-  Substitue d in equation 5
      1(0.7) + 1m = 1.8
      0.7 + 1m = 1.8
      1m = 1.8 - 0.7
       1m = 1.1
5.- Subtitute m in equation 4
      1t = 2.40 - 1(1.1)
      1t = 2.40 - 1.1
       1t = 1.3
6.- Result
      1 tulip + 3 daisies + 2 mums cost = 1.3 + 3(0.7) + 2(1.1)
                                                             = 1.3 + 2.1 + 2.2
                                                             = $5.6