4000-1-2-3-4-5-… -76-77-78=______ ．

4000-1-2-3-4-5-… -76-77-78=______ ．

4000-1-2-3-4-5-… -76-77-78=4000-（1+2+3+4+5-… +76 + 77 + 78) = 4000 - (1 + 78) × 78 △ 2 = 4000-79 × 78 △ 2 = 4000-3081 = 919

1+2+3+4+5+6+…… +How much is 78 + 79 + 80? There must be a calculation process. We need to explain why it is so calculated

1+2+3+4+5+6+…… +78+79+80
=(1+80)x80÷2
=81x40
=3240

How much is 7 / 18 times 0.24?

28 / 3

How to solve that x minus 4 / 7 equals 4 / 7

X-4 / 7 = 4 / 7
X = 4 / 7 + 4 / 7
X = 8 / 7

(negative 8 and 3 / 7) + (negative 7.5) + (negative 21 and 3 / 7) + (+ 3 and 1 / 2)

It's minus 33 and six seventh

How much is minus seven plus five and one-half plus minus three and one-half plus four,

=-7+11/2+(-7/2)+4
=-7+2+4
=-1

(- 8 and 3 / 7) + (- 7.5) + (- 21 and 7 / 4) + (- 3 and 1 / 2)

(- 8 and 3 / 7) + (- 7.5) + (- 21 and 7 / 4) + (- 3 and 1 / 2)
=-8-3/7-7-1/2-21-4/7+3+1/2
=-33-1+1
=-33

(- 1 and 2 / 3) + 1 and 2 / 1 + 7 and 4 / 1 + - 2 and 4 / 1 + negative 2 and 3 / 1 + negative 8 and 2 / 1 =? More details

(- 1 and 2 / 3) + 1 and 2 / 1 + 7 and 4 / 1 + - 2 and 4 / 1 + negative 2 and 3 / 1 + negative 8 and 2 / 1
=[(- 1 and 2 / 3) + (negative 2 and 1 / 3)] + [1 and 1 / 2 + negative 8 and 1 / 2] + [7 and 1 / 4 + (- 2 and 1 / 4)]
=(-4)+(-7)+5
=-6

(minus a minus two-thirds) × a minus two-fifths equals minus one

-2/(a-2)*2/(a-5)=-1
After simplification, a Λ 2-7a + 6 = 0
Then multiply (A-1) * (a-6) = 0 with cross phase
Finally, a = 1, a = 6

（1/9-1/6-1/18）×36=
To calculate the process

Multiply 36 in
=(1/9)×36-(1/6)×36-(1/18)×36=4-6-2=-4