Ответ:

3)

[tex](-3.25-(-1.75)):(-0.6) + 0.8*(-7) = (-3.25+1.75):(-0.6) + 0.8*(-7)=(-1.5):(-0.6) + 0.8*(-7) = 2.5+ 0.8*(-7) = 2.5-5.6 = -3.1[/tex]

4)

[tex]-0.6(16b-5) - (2.9b-8) -4(4-1.5b) = -9.6b+3 - (2.9b-8) -4(4-1.5b) = -9.6b+3 - 2.9b+8 -4(4-1.5b) = -12.5b+11 - 4(4-1.5b) = -12.5b+11-16+6b = -6.5b-5\\b= -\frac{9}{13} \\ -6.5b-5 = -6\frac{1}{2} * ( -\frac{9}{13} ) -5 = \frac{13}{2} * \frac{9}{13} - 5 = 4.5 - 5 = 0.5[/tex]

5)

[tex]4(5x-3y)-6(3x-y) = 20x-12y - 18x+6y = 2x-6y = -2*(3y-x)\\3y-x = 2.1\\-2*(3y-x) = -2*2.1 = -4.2[/tex]