26 - 21 = 5 or 24 - 23 = 1
(10+9)+(1−1)+(2−2)+(3−1)+(4−4) = 21This is the same equation rewritten: (10+9)+(3−1) = 21This can be done as 1-1, 2-2, 4-4 cancel themselves out.
1/3 + 2/7 = 7/21 + 6/21 = 13/21
21, sigh.
2/3 + 1/7 + 4/6 = 14/21 + 3/21 + 14/21 = 31/21 = 1 10/21
2+1= 21 joking, it is 3
26 - 21 = 5 or 24 - 23 = 1
(10+9)+(1−1)+(2−2)+(3−1)+(4−4) = 21This is the same equation rewritten: (10+9)+(3−1) = 21This can be done as 1-1, 2-2, 4-4 cancel themselves out.
1/3 + 2/7 = 7/21 + 6/21 = 13/21
1 + 2 + 3 + 4 + 6 + 7 + 12 + 14 + 21 + 28 + 42 = 140
21, sigh.
2/3 + 1/7 + 4/6 = 14/21 + 3/21 + 14/21 = 31/21 = 1 10/21
96
1/2 + 1/3 * 1/7 = 1/2 + 1/21 = 21/42 + 2/42 = 23/42
x=1/2(-1-square root of 21) and x=1/2(square root of 21 -1)
12 + 9 = 21. 21/10 =2 and 1/10 (21 divided by 10).
As posed, the question has no answer in base 10 arithmetic.The largest digit is 9 and 9 + 1 + 2 + 3 + 1 = 16, which is way short of 21.There is no solution for other integer bases either.