Question

[nguyen minh ngoc]

a)   (3/4 + x ) × 7/4 - 5 = 7/6

b)    X × 12 + 13 × x + x ÷ 2 + 195 =1995

c)    (x + 1 ) + (x + 4 ) + (x + 7) + ...... + ( x + 28 ) = 156

Answer 1

[Dương Lam Hàng]

a) \(\left(\frac{3}{4}+x\right)\times\frac{7}{4}-5=\frac{7}{6}\)

\(\Leftrightarrow\left(\frac{3}{4}+x\right)\times\frac{7}{4}=\frac{37}{6}\)

\(\Leftrightarrow\frac{3}{4}+x=\frac{37}{6}:\frac{7}{4}=\frac{74}{21}\)

\(\Leftrightarrow x=\frac{74}{21}-\frac{3}{4}=\frac{233}{84}\)

Vậy ....

b) \(x\times12+13\times x+x:2+195=1995\)

\(\Leftrightarrow x\times12+x\times13+x\times0,5=1800\)

\(\Leftrightarrow x\times\left(12+13+0,5\right)=1800\)

\(\Leftrightarrow x\times25,5=1800\)

\(\Leftrightarrow x=\frac{1200}{17}\)

c) (x+1)+(x+4)+(x+7)+....+(x+28) = 156

<=> (x+x+x+...+x)+(1+4+7+...+28) = 156

<=> 10x    + 145      = 156

<=> 10x         = 11

<=> x            = 1,1

Vậy ...