Q. The Sum of the angles of a triangle is 180°. If the three angle are (2x + 15)°, 85°, (x + 20)°, the value of x is.

 Q. The Sum of the angles of a triangle is 180°. If the three angle are (2x + 15)°, 85°, (x + 20)°, the value of x is.

Solution:-

Sum of the all angles of Triangle is 180°.

According to that 

                        (2x + 15)° + 85°+ (x + 20)° = 180°

                       ( 2x + x )° + (15 + 85 + 20)° = 180°

                        3x + 120° = 180°

                        3x = 180° - 120°

                        3x = 60°

                        x = 60/3

                        x = 20° Ans 

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Key Facts:- 

• A statement of equality like 6 + x = 11, which contains an unknown quantity is called an equation.
• Statement like x < 4 and x >  7 are called inequalities or in equations.
• Any equation consists of left side, an equal sign ('=') and a right side.   

                                                            Left side = Right side

• A number which satisfies an equation is called the solution or root of the equation. for e.g. the solution of the equation 5 + x = 7 is 2. In other words, the value of x, called the variable, which makes the given equation a true statement, is the solution of the root of the equation.
• The same number can be added to both sides of an equation. 
• The same number can be subtracted to both sides of an equation. 
• Both sides of an equation can be multiplied by the same number.
• Both sides of an equation can be divided by the same number.
• Any number may be transferred from one side of an equation to the other if we change its sign    (+ to -, - to +)