[ratio and proportion][section 49]
(1.) 7/8 = x/40 here is the problem
8x = 280 cross multiply
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8 8
divide each side by 8
x = 35 divide and cancel
(2.) 9/2 = 63/x here is the problem
9x = 126 cross multiply
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9 9 divide each side by 9
x = 14 divide and cancel
(3.) 11/x = 132/24 here is the problem
132x = 264 cross multiply
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132 132
divide each side by 132
x = 2 divide and cancel
(4.) x/13 = 10/65 here is the problem
65x = 130 cross multiply
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65 65
divide each side by 65
x = 2 divide and cancel
(5.) 21/5 = x/2.5 here is the problem
5x = 52.5 cross multiply
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5 5 divide each side by 5
x = 10.5 divide and cancel
(6.) 29/7 = x/1.75 here is the problem
7x = 50.75 cross multiply
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7 7 divide each side by 7
x = 7.25 divide and cancel
(7.) 17/2 = 8.5/x here is the problem
17x = 17 cross multiply
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17
17 divide each side by
17
x = 1 divide and cancel
(8.) (b + 3)/5 = 7/10 here is the problem
10b + 30 = 35 cross multiply
-30 -30
subtract 30 from each side
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10b =
5 subtract
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10 10 divide each side by 10
b = 1/2 reduce and cancel
(9.) 3/z = 8/(z + 5) here is the problem
8z = 3z + 15 cross multiply
-3z -3z subtract 3z from each side
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5z = 15 subtract
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5 5 divide each side by 5
z = 3 divide and cancel
(10.) (r + 4)/2 = (r - 3)/1 here is the problem
2r - 6 = r + 4 cross multiply
+ 6
+ 6 add 6 to each side
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2r = r + 10
add
-r -r subtract r from each side
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r =
10 subtract