How to simplify the problem of 15 × 19 of 23 + 19 × 8 of 23?

How to simplify the problem of 15 × 19 of 23 + 19 × 8 of 23?

15 × 19 of 23 + 19 × 8 of 23
=19 × 15 of 23 + 19 × 8 of 23
=19 of 23 × (15 + 8)
=19 / 23 × 23
=19

How many of them are 20% 1, 24% 1, and how many% 1

One and three fifths = 8 / 5
(8/5)/(1/20)=32
(8/5)/24=1/15
(8/5)/(1/100)=160

199 + 195 + 191 + ··· + 3 is equal to?

The one above still uses the arithmetic sequence. Well, it's not detailed. I'll write it again with the arithmetic sequence
The formula of the first difference of sequence and Sn = 2
A1 is the first item, which is 3,
An is the last term, 199,
Now there are several requirements
If the difference between two adjacent numbers is 4, then n = (199-3) / 4 + 1 = 50
Next, substitute several numbers into the first n terms and formula above, and the sum is 5050
But the arithmetic sequence is only learned in high school, you see, it should use your knowledge to do out of the method