a-b=-4

\(\Rightarrow\)2a-2b=-8

\(\Rightarrow\)a+2b+2a-2b=11-8

\(\Rightarrow\)3a=3

\(\Rightarrow\)a=1

\(\Rightarrow\)b=a+4=1+4=5

\(\Rightarrow\)4a-b=1.4-5=4-5=-1

a) 3x (12x - 4) - 9x (4x - 3) = 30

\(\Leftrightarrow\)36x²  – 12x – 36x²  + 27x = 30

\(\Leftrightarrow\)15x = 30

\(\Leftrightarrow\)x = 2

b) x (5 - 2x) + 2x (x - 1) = 15

\(\Leftrightarrow\)5x – 2x^​2  + 2x²  – 2x = 15

\(\Leftrightarrow\)3x = 15

\(\Leftrightarrow\)x =5

1+2+3+4+5+6+7+8

=(2+8)+(3+7)+(4+6)+1+5

=10+10+10+6

=10.3+6

=30+6

=36

So the answer is 36

1+2+3+4+5+6+7+8

=(2+8)+(3+7)+(4+6)+1+5

\(\dfrac{3}{m}=\dfrac{27}{72}\\\Leftrightarrow \dfrac{3.9}{9m}=\dfrac{27}{72}\\\Leftrightarrow \dfrac{27}{9m}=\dfrac{27}{72}\\ \Rightarrow9m=72\\ \Rightarrow m=8\)

23 rows of 27 chairs each

So 23.27=621 (chairs)

So there are 621 chairs in the room

The absolute difference between the length and width of rectangle MNOP​ is |(4x+9)-(4x-3)|

=|4x+9-4x+3|

=|12|

=12

So the answer is 12

2011^x=x²⁰¹¹

So 2011²⁰¹¹=x^​x

So x=2011

2^x+2^y+2^​z=1024

^​but 1024=512+256+256

so \(\left[{}\begin{matrix}\left\{{}\begin{matrix}x=9\\y=8\\z=8\end{matrix}\right.\\\left\{{}\begin{matrix}x=8\\y=9\\z=8\end{matrix}\right.\\\left\{{}\begin{matrix}x=8\\y=8\\z=9\end{matrix}\right.\end{matrix}\right.\)

x^​2​+x+1\(\ne\)0 with any value of x

So don't have any value of x satisfy

So don't have any value of A

So A\(\in\)\(\varnothing\)

1+2+3+10000000

=(1+2+3)+10000000

=6+10000000

=10000006

10+20+30+40+50+60+70+80+90

=(10+90)+(20+80)+(30+70)+(40+60)+50

=100+100+100+100+50

=100.4+50

=400+50

=450

x:3:2=9

\(\Leftrightarrow x=9.2.3\)

\(\Leftrightarrow x=54\)

So the answer is 54

S dodecagon = S original rectangle - S removed squares

S original rectangle = 4.5=20 (cm²)

S removed squares = 1².4=4 (cm​²)

So S dodecagon = 20-4=16 (cm²)

20+30+40+50+60+70

=(20+30+50)+(40+60)+70

=100+100+70

=100.2+70

=200+70

=270

So the answer is 270

=(1+9)+(2+8)+(3+7)+(4+6)+10+5

=10+10+10+10+10+5

=10.5+5

=50+5

=55

So the answer is 55

99999.55555

=(100000-1).55555

=5555500000-55555

=5555444445

40%\(\times\dfrac{1}{3}\times24\div0,8\)

=\(\dfrac{40.1.24}{100.3}\div\dfrac{4}{5}\)

=\(\dfrac{16}{5}.\dfrac{5}{4}\)

= 4

So the answer is 4

we have : 0,0A=\(\sqrt{0,0049}\)

but \(\sqrt{0,0049}=0,07\)

\(\Rightarrow0,0A=0,07\)

\(\Rightarrow A=7\)

So the value of A is 7

a,x=100-33=67

b,x=100-88=12

c,x=100-22=78

d,x=100-18=82