a,X+X:3x4,5+X:2x7=252

X+Xx1,5+Xx7/2=252

Xx(1+1,5+7/2)=252

Xx6=252

X=42

b, (515,5x40-18)x(314:0,5xX)=17776

(20620-18)x(628xX)=17776

20602x(628xX)=17776

628 x X=17776:20602

ko bt nữa....

X + X : 3 x 4,5 + x : 2 x 7 = 252

<=> X (1 + 3/2 + 7/2) = 252

=> X x 6 = 252

=> X = 252 : 6

=> X = 42

a. 35

b. 90

X + X : 3 = 60

=> X.(1 + 1/3) = 60

=> X . 4/3 = 60

=> x = 60 : 4/3 

=> X = 45

18 x y- y : 0,125 +y x 0,5 - 2 x y x 0,15 =18

18 x y - y x 8 + y x 0,5 - y x 0,3 =18

y x (18-8+0,5-0,3)=18

y x 10,2=18

y= \(\frac{30}{17}\)

\(18\times y-y:0,125+y\times0,5-2\times y\times0,15=18\)

\(\Rightarrow18\times y-y\times8+y\times\frac{5}{10}-2\times y\times0,15=18\)

\(\Rightarrow18\times y-y\times8+y\times\frac{1}{2}-2\times y\times\frac{15}{10}=18\)

\(\Rightarrow18\times y-y\times8+y\times2-2\times y\times\frac{3}{2}=18\)

Tự tìm nhé

B=18=>A=9

0,5 x y + 1,4 x y = 106,78

1,9 x y = 106,78

        y = 106,78 : 1,9

       y = 56,2

\(7,75-\left(0,5\times y\div5-6,2\right)=5\)

\(0,5\times y\div5-6,2=7,75-5=2,75\)

\(0,5\div5\times y-6,2=2,75\)

\(0,1\times y=2,75+6,2=8,95\)

\(\dfrac{1}{10}y=8,95\)

\(y=8,95\times10=89,5\)

\(y\div6\times7,2+1,3\times y+y\div2+15=19,95\)

\(1,2\times y+1,3\times y+0,5y=19,95-15=4,95\)

\(y\left(1,2+1,3+0,5\right)=4,95\)

\(2y=4,95\)

\(y=4,95\div2=2,475\)