Помогите срочно!!!Номер 623(2,4),632(5)!!!20б

623)
2)
$\frac{6.8 - 7 +8 }{5.4 - 6.7} \\\\ 5.4 - 6.7 = - 1.3\\ 6.8-7+8 = 6.8 + 1 = 7.8\\\\ \frac{6.8 - 7 +8 }{5.4 - 6.7} = \frac{7.8}{-1.3} = -6$

4)
$\frac{0.6*(-9) - 3.6}{-1.5*4}\\\\ 0.6*(-9) - 3.6 = -5.4 -3.6 = -9\\ -1.5*4 = -6\\\\ \frac{0.6*(-9) - 3.6}{-1.5*4} = \frac{-9}{-6} = 1.5$

632)
2)
$b = 4\\ (9.3b-1.5b):(-6) = (9.3*4-1.5*4):(-6)=(37.2-6):(-6)=31.2:(-6)=-5.2$

$\\b = -5\\(9.3b-1.5b):(-6) = (9.3*(-5)+1.5*5):(-6)=-39:(-6)=6.5$