(X x 3 - 0,8) : X + 14,5 = 15

3*x-0/x-70=15

3*x-0=85

3*x=85

x=85/3

a ) \(x+x\times\frac{1}{3}\div\frac{2}{9}+x\div\frac{2}{7}=252\)

\(x\times1+x\times\frac{1}{3}\div\frac{2}{9}+x\div\frac{2}{7}=252\)

\(x\times1+x\times\frac{1}{3}\times\frac{9}{2}+x\times\frac{7}{2}=252\)

\(x\times1+x\times\frac{9}{6}+x\times\frac{7}{2}=252\)

\(x\times\left(1+\frac{9}{6}+\frac{7}{2}\right)=252\)

\(x\times6=252\)

\(x=252\div6\)

\(x=42\)

b ) \(\left(3\times x-0,8\right)\div x+14,5=15\)

\(\left(3\times x-0,8\right)\div x=15-14,5\)

\(\left(3\times x-0,8\right)\div x=0,5\)

\(0,8\div x=3-0,5\)

\(0,8\div x=2,5\)

\(x=0,8\div2,5\)

\(x=0,32\)

( 3 x - 0.8 ) : x + 14.5 = 15

( 3 x - 0.8 ) x \(\frac{1}{x}\)+ 14,5 = 15

3X x \(\frac{1}{x}\)- 0,8 x \(\frac{1}{x}\)= 0,5

\(\frac{3x}{x}-\frac{0,8}{x}=\frac{0,5x}{x}\)

=> 3x - 0,8 = 0,5x

     3x - 0,5x = 0,8

       2,5x = 0,8

            x = 2,5 : 0,8

            x = \(\frac{25}{8}=3,125\)

\(\frac{9x-0,7}{4}-\frac{5x-1,5}{7}=\frac{7x-1,1}{6}-\frac{5\left(0,4-2x\right)}{6}\)

\(\Leftrightarrow\frac{\left(9x-0,7\right)\cdot7}{4\cdot7}-\frac{\left(5x-1,5\right)\cdot4}{7\cdot4}=\frac{7x-1,1-2+10x}{6}\)

\(\Leftrightarrow\frac{63x-4,9-20x+6}{28}=\frac{7x-1,1-2+10x}{6}\)

\(\Leftrightarrow\left(63x-4,9-20x+6\right)\cdot6=28\left(7x-1,1-2+10x\right)\)

\(\Leftrightarrow378x-120x+6,6=196x-86,8+280x\)

\(\Leftrightarrow378x-120x-196x-280x=-86,8-6,6\)

\(\Leftrightarrow-218x=-93,4\)

\(\Leftrightarrow x=\frac{467}{1090}\)

\(a)4(15-18)-(3-5).(-3)^2\)

\(=4.\left(-3\right)-2.9\)

\(=6\)

\(b)(-4-11):(-3)\)

\(=-15:\left(-3\right)\)

\(=5\)

\(c)143-(-57)-(-2)^3.(-3)^0\)

\(=143+57+8.1\)

\(=208\)

\(d,\left(-5\right).\left[\left(90-2.5\right)-10^2+10:\left|-2\right|\right]\)

\(=-5.\left[80-100+10:2\right]\)

\(=-5.-15\)

\(=75\)