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For the rational number A.B, define and calculate a & B = 3A + B / a-3b, calculate: (- 2) & (7 & (- 6)) & = a sign (plus sign, minus sign, multiplication sign, division sign)
7&（-6）
That is, a = 7, B = - 6
7&（-6）=(21-6)/(7+18)=3/5
So (- 2) & 7 & 6)
=（-2）&（3/5）
=（-6+3/5）/（-2-9/5）
=27/19
Column formula calculation, you can use the equation!
Car a and car B are facing each other from the East and West. Car a travels 47.5 kilometers per hour and car B 42.5 kilometers per hour. The two cars meet 20 kilometers from the midpoint. How many kilometers are there between the East and West?
Let only one unknown
Suppose that the two cars meet after t hours. When they meet, a travels 20 * 2 = 40 kilometers more
（47.5-42.5）T=40
T=8
The distance between the two places is (47.5 + 42.5) * 8 = 720km
During the break, Beibei counted. There are 26 students playing table tennis on eight table tennis tables, some playing singles and some playing doubles. Please count how many students are playing doubles
According to the meaning of the question, the number of doubles pieces is: (26-2 × 8) / (4-2), = 10 / 2, = 5 (pieces); 5 × 4 = 20 (people). Answer: there are 20 people playing doubles
Column synthesis formula or equation calculation
(1) Number a is 80, 16 less than 4 / 5 of number B. what's number B?
Let B be X
x*(4/5)-16=80
x*(4/5)=96
x=120
A: the number B is 120
(80+16)/(4/5)=120
A: the number B is 120
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