mark is 6 years older rhan his sister mackenzie.hos brother steve is 3 years younger than his sister mackenzie.the sum of their ages is 81. how old is steve?

Answer 1

Let mr represent Mark, mc represent Mackenzie and s represent Steve. We can write a few expressions to represent this problem and solve via substitution:

mr = mc + 6

s = mc - 3

mr + mc + s = 81

Now we can solve by substitution

mr + mc + s = 81

(mc + 6) + mc + (mc - 3) = 81

3mc + 3 = 81

3mc = 78

mc = 26

Now that we know Mackenzie is 26 years old, we can Steve's age:

s = mc - 3 = 26 - 3 = 23

Steve is 23 years old.

Answer 2

Let S = Sister's (Mackenzie's) age

Let M = Mark's age = S + 6

Let B = Brother's (Sreve's) age = S - 3

Sum of the ages is 3S + 3 = 81

3S = 78

S = 26 (Mackenzie)

M= 32 (Mark)

B = 23 (Steve)