5.
Let x be the age of the father and y be the age of the son. As of today, he's 3 times older, so we have 
10 years ago their ages were, respectively, x-10 and y-10, and the father was 5 times older: 
So, we have the system
Using the first equation, we can substitute every occurrence of "x" with "3y" in the second equation:
So, the son is 20 years old, which means that the father is 60 years old.
Indeed, 10 years ago they were 10 and 50 years old, so the father was 5 times older.
6.
Let x be the age of the grandfather and y the age of the granddaughter. We know that the grandfather is 10 times older: 
He also is 54 years older: 
Again, if we substitute x=10y in the second equation we have
Answer: 0
Step-by-step explanation:
Add −66 and 66. 0
Answer:
2(2x-3) or 4x-6 if you want to sound smarter
Step-by-step explanation:
I did it
Step-by-step explanation:
Part A :-
m(a) , m(b) & m(c) when will get combined ; they will form a straight angle (180°) .
So,
m(a) + m(b) + m(c) = 180°
=> 3x + 5 + 5x - 18 + 7x - 2 = 180°
=> 15x - 15 = 180°
=> 15(x - 1) = 180°
=> x - 1 = 180 / 15
= 12°
=> x = 12 + 1
= 13°
Using the value of x gives the value of m(a) , m(b) & m(c) .
• m(a) = 3 × 13 + 5 = 39 + 5 = 44°
• m(b) = 5 × 13 - 18 = 65 - 18 = 47°
• m(c) = 7 × 13 - 2 = 91 - 2 = 89°
Part B :-
Complementary angles are the pair of angles whose sum is 90° . Here sum of m(a) & m(b) is
44 + 47 = 91°. Hence they are not complementary angles.
