[tex] \frac{7}{9} [/tex] от 81
45% от 70
число, [tex] \frac{5}{9} [/tex] которого равны 45
[tex]5(x - 2) - (x - 1) = 9[/tex]

http://znanija.com/task/11880075

7/9 * 81 = 7 * 9 = 6370 * (45/100) = 70 * 0.45 = 31.545 * 9/5 = 9 * 9 = 815x - 10 - x +1 = 94x - 9 = 94x = 9 + 94x = 18x = 4.5

81*7/9=6370*0,45=31,545:5/9=45*9:5=815х-10-х+1=94х=18х=18:4х=4,5