$122×4= $
$110×5= $
$224×20= $
$214×20= $
$22×300= $
$13×300= $
$15×400= $
$81×400= $
$140×20= $
$32×200= $
$214×30= $
$13×200= $
$112×30= $
$124×20= $
$312×30= $
$412×40= $
$317×100= $
$313×30= $
$112×20= $
$503×30= $
$48×50= $

解析：这些题目都是基础的乘法口算题，需要直接计算出各个乘法表达式的结果。
答案：
$122×4= 488$
$110×5= 550$
$224×20= 4480$
$214×20= 4280$
$22×300= 6600$
$13×300= 3900$
$15×400= 6000$
$81×400= 32400$
$140×20= 2800$
$32×200= 6400$
$214×30= 6420$
$13×200= 2600$
$112×30= 3360$
$124×20= 2480$
$312×30= 9360$
$412×40= 16480$
$317×100= 31700$
$313×30= 9390$
$112×20= 2240$
$503×30= 15090$
$48×50= 2400$

连线。
| $12×50$ | $390$ |
| $22×30$ | $280$ |
| $32×20$ | $330$ |
| $13×30$ | $640$ |
| $14×20$ | $660$ |
| $11×30$ | $600$ |
| $210×3$ | $6330$ |
| $110×4$ | $4400$ |
| $1220×3$ | $2660$ |
| $1330×2$ | $3660$ |
| $2200×2$ | $440$ |
| $2110×3$ | $630$ |
| $124×20$ | $2480$ |
| $214×20$ | $2300$ |
| $121×30$ | $3690$ |
| $324×20$ | $6480$ |
| $123×30$ | $3630$ |
| $115×20$ | $4280$ |
| $142×20$ | $2840$ |

解析：本题考查多位数乘两位数的口算方法。
首先，我们计算每一对乘法的结果：
$12×50 = 600$，
$22×30 = 660$，
$32×20 = 640$，
$13×30 = 390$，
$14×20 = 280$，
$11×30 = 330$，
$210×3 = 630$，
$110×4 = 440$，
$1220×3 = 3660$，
$1330×2 = 2660$，
$2200×2 = 4400$，
$2110×3 = 6330$，
$124×20 = 2480$，
$214×20 = 4280$，
$121×30 = 3630$，
$324×20 = 6480$，
$123×30 = 3690$，
$115×20 = 2300$，
$142×20 = 2840$。
然后，将计算结果与给出的数字进行匹配并连线：
$12×50$ 连 $600$，
$22×30$ 连 $660$，
$32×20$ 连 $640$，
$13×30$ 连 $390$，
$14×20$ 连 $280$，
$11×30$ 连 $330$，
$210×3$ 连 $630$，
$110×4$ 连 $440$，
$1220×3$ 连 $3660$，
$1330×2$ 连 $2660$，
$2200×2$ 连 $4400$，
$2110×3$ 连 $6330$，
$124×20$ 连 $2480$，
$214×20$ 连 $4280$，
$121×30$ 连 $3630$，
$324×20$ 连 $6480$，
$123×30$ 连 $3690$，
$115×20$ 连 $2300$，
$142×20$ 连 $2840$。