20．
0 160502 160510 160516 160520 160526 160528 160532 160538 160540 160546 160552 160556 160558 160562 160568 160570 160576 160580 160582 160586 160588 160592 160594 160596 160597 160598 160600 160601 160602 160604 160606 160610 160612 160616 160618 160622 160628 160630 160636 160640 160642 160646 160652 160658 160660 160666 160670 160672 160678 160682 160688 160696 199269
| $\frac{1}{4}$+$\frac{1}{5}$ | $\frac{1}{4}$-$\frac{1}{5}$ | $\frac{1}{4}$×$\frac{1}{5}$ | $\frac{1}{3}$÷$\frac{1}{2}$ |
| $\frac{1}{3}$×$\frac{1}{2}$ | $\frac{1}{2}$-$\frac{1}{3}$ | $\frac{8}{15}$×$\frac{3}{4}$ | $\frac{7}{8}$÷7 |
| $\frac{1}{3}$+$\frac{1}{4}$ | $\frac{2}{3}$-$\frac{1}{4}$ | 5÷$\frac{5}{6}$ | 6-$\frac{7}{8}$-$\frac{1}{8}$． |
一个正方体6个面分别写着1，2，3，4，5，6．根据如图摆放的三种情况，写出数字6对面的数字是2．