1)
3*(x-5)=7*12-4*(2x-11)
3x-15=84-8x+44
3x-15=128-8x
3x+8x=128+15
11x=143
x=143:11
x=13
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2)
5*3+7x-12=3*(x+13)
15+7x-12=3x+39
3+7x=3x+39
7x-3x=39-3
4x=36
x=36:4
x=9
260 : 2 = 130
130 : 2 = 65
65 : 5 = 13
13 : 13 = 1
260 = (2*2) * 5 * 13 = 2^2 * 5 * 13
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Пояснения: 2^2 - два во второй степени
А) 73 +112 = 185: 16 = 11. 5.625
б) 69 * 190 = 13. 110 68.250: 65 = 1.050 13.110 - 6.843 = 6.267 + 1.050 = 7.317