a: =(7h99'):3=519':3=173'

b: =345px8=2760p

c: =4h13p+194p=447p

Câu 1: 

0,9 x 218 x 2 + 0,18 x 4290 + 0,6 x 353 x 3

= 9/10 x 436 + 9/50 x 4290 + 6/10 x 1059

= 9 x 43,6 + 9 x 85,8 + 6 x 105,9

= 3 x 130,8 + 3 x 257,4 + 3 x 211,8

= 3 x ( 130,8 + 257,4 + 211,8 )

= 3 x 600 

= 1800

Câu 2: 

3/4 x X + 1/2 x X - 15 = 35

X x ( 3/4 + 1/2 ) - 15 = 35

X x ( 3/4 + 1/2 ) = 50

X x 5/4 = 50

X = 40

13 x (x - 7) = 5 x X + 13

 13 x X - 13 x 7 = 5x + 13 (5x tuc la 5 x X)

 13x - 91 = 5x + 13

 13x - 5x = 91 + 13

 8x = 104

x = 104 : 8

x = 13

ý b

Bài giải :
a, ( 3 - y ) x 15 = 0

      3 - y          = 0 : 15

      3 - y          = 0

      y               = 3 - 0

      y                = 3

b, 13 x ( y - 10 ) = 13

             y - 10   = 13 : 13

              y - 10   = 1

               y         = 1 + 10

               y          = 11