1) 32:(13-5*x)=4
13-5*x =32 *4
8*x= 128
x= 128:8
x=1
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2) 3*x -15 : 3=19 +3
3*x-5=21
3x =21* 5
3x=105
x= 105 :3
x=9
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3) 5*x-21:7=4+13
5*x -3 = 17
5x =17 *3
5x = 51
x= 51*5
x=4
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4) 7