Ta có : (1 + y) + (4 + y) + (7 + y) + ...... + (28 + y) = 156
=> (y + y + ..... + y) + (1 + 4 + 7 + ..... + 28) = 156
=> 10y + 145 = 156
=> 10y = 11
=> y = 11/10
\(\left(1+y\right)+\left(4+y\right)+\left(7+y\right)+...+\left(28+y\right)=156\)
\(\left(1+4+7+...+28\right)+\left(y+y+y+y+...+y\right)=156\)
\(145+10y=156\)
\(10y=156-145\)
\(10y=11\)
\(y=11\div10\)
\(y=1,1\)
\(\left(1+y\right)+\left(4+y\right)+\left(7+y\right)+....+\left(28+y\right)=156\)
\(\left(1+4+7+...+28\right)+10x=156\)
\(145+10x=156\)
\(10x=156-145\)
\(10x=11\)
\(\Rightarrow x=1,1\)
(1+y)+(4+y)+(7+y)+....+(28+y)=156
(1+4+7+...+28)+10x=156
145+10x=156
10x=156−145
10x=11
⇒x=1,1
Anh em trả lời hộ tớ bài; 16:[(3/5y+8):21+9]=7/10