How to solve ninth grade math problems with simple calculation

9x+ 12 x = 2 1 The process of solving the equation is as follows:

9x+ 12ⅹ=2 1

Solution:

(9+ 12)x=2 1

2 1x=2 1

x= 1

So 9x+ 12 x = 2 1 The final result of solving the equation is x= 1.

Extended data:

Two solutions of binary linear equation;

1, addition, subtraction and elimination

Example: Solve the system of equations x+y=9① x-y=5②.

Solution: ①+②, 2x= 14, that is, x=7.

Bring x=7 into ① to get 7+y=9 and y=2.

∴x=7,y=2

2. Substitution elimination

Example: Solve the system of equations x+y = 5 16x+ 13y = 89②.

Solution: Take ③ from ① with x=5-y③ to ② to get 6(5-y)+ 13y=89 and y=59/7.

Bring y=59/7 into ③ to get x=5-59/7, that is, x=-24/7.

∴x=-24/7,y=59/7

Elimination method: the unknowns in the equation are solved one by one from more to less.