A math problem in the third grade of primary school: the number of roosters in the henhouse is three times that of hens, and the number of roosters is more than that of hens 18. How many cocks and hens are there in the henhouse? When the number of hens is 9, the number of cocks is 27.

Solution: If the number of hens is X, the number of cocks is 3x.

Because there are more cocks than hens 18, it can be listed as 3x-x= 18.

x=9 3x=27

Answer: If the number of hens is 9, the number of cocks is 27.

Extended data:

Historical evolution of linear equation with one variable;

In the 9th century A.D., Arab mathematician Hua Lazimi gave simple and feasible basic methods to understand equations, namely "reduction" and "elimination". But no alphabetic symbols are used. It embodies the obvious idea of the equation.

/kloc-in the 3rd century, China's complementary technique was introduced to Europe, and the Italian mathematician Fibonacci used single hypothesis and double hypothesis to solve linear equations in his book Calculation.

/kloc-in the 6th century, after David founded symbolic algebra, he put forward such propositions as shifting term and equation division, and also created this concept, which was honored as "the father of modern mathematics". But Vida doesn't accept negative numbers.

/kloc-in the 6th century, Cheng Dawei (1533- 1606), a mathematician in the Ming dynasty, also used the hypothesis method to solve a linear equation.

1859, Chinese mathematician Li officially translated this kind of equations into linear equations.

References:

Baidu encyclopedia-unary linear equation