Find the value of x in each of the following proportions. a. 6 : 9 = x : 72 b. 8⁄3 = 40⁄x c. x : 55 = 3 : 5 d. 33⁄7 = 11⁄5

Part (a):
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6 : 9 = x : 72

By using cross multiplication 
∴ 9 x = 6 * 72
∴ 9 x = 432
∴ x = 432/9 = 48
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Part (b):
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8 : 3 = 40 : x

By using cross multiplication 
∴ 8x = 3 * 40

∴ 8x = 120
∴ x = 120/8 = 15
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Part (c):
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x : 55 = 3 : 5

By using cross multiplication 
∴ 5 x = 3 * 55
∴ 5 x = 165
∴ x = 165/5 = 33
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Part (d):
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33 : x = 11 : 5

By using cross multiplication 
∴ 11 x = 5 * 33
∴ 11 x = 165
∴ x = 165/11= 15
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