Multiply of 37 by multiplies of 3:
3 x 37 = 111
6 x 37 = 222
9 x 37 = 333
12 x 37 = 444
15 x 37 = 555
18 x 37 = 666
21 x 37 = 777
24 x 37 = 888
27 x 37 = 999

Nice one:
111.111.111 x 111.111.111 = 12.345.678.987.654.321

Trapeze:
1 x 9 + 2 = 11
12 x 9 + 3 = 111
123 x 9 + 4 = 1111
1234 x 9 + 5 = 11111
12345 x 9 + 6 = 111111
123456 x 9 + 7 = 1111111
1234567 x 9 + 8 = 11111111
12345678 x 9 + 9 = 111111111

another Trapeze:
1 x 8 + 1 = 9
12 x 8 + 2 = 98
123 x 8 + 3 = 987
1234 x 8 + 4 = 9876
12345 x 8 + 5 = 98765
123456 x 8 + 6 = 987654
1234567 x 8 + 7 = 9876543
12345678 x 8 + 8 = 98765432
123456789 x 8 + 9 = 987654321

and another one:
0 x 9 + 8 = 8
9 x 9 + 7 = 88
98 x 9 + 6 = 888
987 x 9 + 5 = 8888
9876 x 9 + 4 = 88888
98765 x 9 + 3 = 888888
987654 x 9 + 2 = 8888888
9876543 x 9 + 1 = 88888888
98765432 x 9 + 0 = 888888888
987654321 x 9 – 1 = 8888888888
9876543210 x 9 – 2 = 88888888888

try these

1 2 3 4 5 6 9 (估一成語)
1000 × 1000 = 100 × 100 × 100 (估一成語) 成千上萬
3, 5, 5, 3, 5, 3 (估一成語) 三五成群
3, 3, 3, 2, 2 (估一成語) 三言兩語
1 + 1 – 1 + 1 – 1 = 1 (估一成語) 先加後減
7086 (估一成語) 七零八落
15 ÷ 2 = (估一成語) 七上八下
20 元 (估一字)
99 (估一字) 白