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5х(у-2)-5(у-2)=5(х-5)*(у-2)
16х-7х=612
16х-7х=9х
9х=612
х=612:9
х=68
-4,2х*(-6у)=25,2ху
Ответ:25,2ху
2/3 = 2х20/3х20 = 40/60
1/2 = 1х30/2х30 = 30/60
3/4 = 3х15/4х15 = 45/60
1/6 = 1х10/6х10 = 10/60
4/15 = 4х4/15х4 = 16/60
7/20 = 7х3/20х3 = 21/60
11/30 = 11х2/30х2 = 22/60
Вроде так