12.在五张完全相同的卡片上,分别写有数字-2,-1,0,1,2,现从中随机抽取一张,抽到写有正数的卡片的概率是( )
| A. | $\frac{1}{5}$ | B. | $\frac{2}{5}$ | C. | $\frac{3}{5}$ | D. | $\frac{4}{5}$ |
11.下列方程变形正确的是( )
0 298190 298198 298204 298208 298214 298216 298220 298226 298228 298234 298240 298244 298246 298250 298256 298258 298264 298268 298270 298274 298276 298280 298282 298284 298285 298286 298288 298289 298290 298292 298294 298298 298300 298304 298306 298310 298316 298318 298324 298328 298330 298334 298340 298346 298348 298354 298358 298360 298366 298370 298376 298384 366461
| A. | 由4+x=7得x=7+4 | B. | 由3x-2(x-1)=8得3x-2x-2=8 | ||
| C. | 由5x=-6得x=-$\frac{5}{6}$ | D. | 由$\frac{x}{7}-\frac{x-1}{8}$=2得8x-7(x-1)=112 |