Recently I had a math course. Here are some interesting problems I selected from my practice history. Solve one problem a day, and do it for 21 days. Then your mathematical ability will greatly improve.

23 - 55 + 51 - 37 - 42 - 36 = ?
52 + 33 + 1 + 83 + 51 - 21 = ?
33 - 83 + 63 - 86 + 34 + 54 = ?
63 + 58 + 5 + 19 - 49 - 38 = ?
22 + 9 - 9 + 14 + 75 - 56 = ?
17 + 45 - 54 - 90 - 67 + 69 = ?
44 - 36 + 92 - 91 + 27 + 12 = ?
99 - 1 - 20 - 2 - 27 - 37 = ?
50 - 52 - 72 - 11 + 96 - 99 = ?
92 + 13 + 84 - 51 + 10 + 42 = ?
31 + 29 + 71 - 21 - 61 - 66 = ?
86 - 12 + 56 + 11 + 29 - 55 = ?
72 - 96 + 45 - 13 + 55 + 75 = ?
24 + 22 + 66 + 44 - 64 - 44 = ?
91 + 15 - 49 + 99 - 62 - 33 = ?
22 - 37 - 17 + 13 + 24 + 38 = ?
37 - 70 + 79 + 89 - 36 + 79 = ?
67 + 65 - 61 - 6 - 68 + 16 = ?
27 - 11 - 64 - 7 - 63 + 21 = ?
34 - 26 - 44 + 55 - 56 + 34 = ?

When you finished them DM me to check if your solutions work out. You can also stress test them offline in your own environment.