Respuesta :
Mark's father is 55. f=55
And this is equal to twice Mark's age plus 15, f=2m+15
Since f=f we can say
2m+15=55 subtract 15 from both sides
2m=40 divide both sides by 2
m=20
So mark is twenty years old.
We can check...
2m+15=55, since m=20 this becomes
2(20)+15=55
40+15=55
55=55
And this is equal to twice Mark's age plus 15, f=2m+15
Since f=f we can say
2m+15=55 subtract 15 from both sides
2m=40 divide both sides by 2
m=20
So mark is twenty years old.
We can check...
2m+15=55, since m=20 this becomes
2(20)+15=55
40+15=55
55=55