Help :/

Here is one way:

   The width is   3   out of   (5+3) = 3/8

      the length is 5 out of  (5+3) = 5/8   

        3/8 x = 45

             x = 120

                5/8 x = 75 cm

Here is a simpler way

   45 is to 3    as   x is to 5

   45/3 = x/5    solve for x

      5 * 45/3 = 75 cm

what about the other question and thank you

t/c = 6/5           (this is given)

t/10 = 6/5

t = 10 * 6/5 = 12        Now you try the 'b' part

6)    L : W = 5 : 3          L : 45 = 5 : 3           L = (5 * 45) / 3          L = 75

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7)           C = 10

T : C = 6 : 5              T : 10 = 6 : 5           T = (10 * 6) / 5       T = 12

P : T = 8 : 3               P : 12 = 8 : 3           P = (12 * 8) / 3         P = 32