B) ( 9 + 12a ) + ( 3a + 7 ) = 76
Let us solve this equation :-
= ( 9 + 12a ) + ( 3a + 7 ) = 76
= 9 + 15a + 7 = 76
= 16 + 15a = 76
[tex]15a = 76 - 16[/tex]
[tex]15a = 60[/tex]
[tex]a = \frac{60}{15} [/tex]
[tex]a = 4[/tex]
Let us check whether it is correct or not :-
= ( 9 + 12 × 4 ) + ( 3 × 4 + 7 ) = 76
= 57 + 19 = 76°
Therefore , the correct option is :-
B) ( 9 + 12a ) + ( 3a + 7 ) = 76
