Make a 10 or 100 to subtract mentally
55-41
14
55-40=15
15-1=14
53-31
50-30=20
458-223
235
78-29
49
78-30=48
48+1=49
65-46
70-50=20
153
86-49=
37
86-50=36
36+1=37
66-19=
70-20=50
1,312-566
746
454-299
155
454-300=154
154+1=155
97-18
100-20=80
1,590-364
1,226