Tìm giá trị y biết y+30%y=−2,3.

Ta có:

 (begin{array}{l}2y + 30% y = – 2,3\2y + dfrac{3}{{10}}y = – dfrac{{23}}{{10}}\dfrac{{23}}{{10}}y = – dfrac{{23}}{{10}}\y = – dfrac{{23}}{{10}}:dfrac{{23}}{{10}}\y = – 1end{array})

Chọn C