Đáp án-Giải thích các bước giải:
$a)$ $150$ $+$ $x$ $=$ $50$ $×$ $2$
$150$ $+$ $x$ $=$ $100$
$x$ $=$ $100$ $-$ $150$
$x$ $=$ $-50$
$b)$ $900$ $+$ $x$ $=$ $300$ $×$ $2$
$900$ $+$ $x$ $=$ $600$
$x$ $=$ $600$ $-$ $900$
$x$ $=$ $-300$
$c)$ $500$ $+$ $x$ $=$ $200$ $×$ $2$
$500$ $+$ $x$ $=$ $400$
$x$ $=$ $400$ $-$ $500$
$x$ $=$ $-100$
#BTS
XIN CTLHN !