Question

Robin’s number is eight more than Sydney’s. The sum of their numbers is 72. What are their numbers?

Answer 1

Assume that Robin's number is r and that Sydney's number is s.

We are given that:
Robin's number is 8 more that Sydney's number
This means that:
r = s + 8 ......> equation I

We are also given that:
The sum of the two numbers is 72
This means that:
r + s = 72 .......> equation II

Substitute with equatiin I in equation II and solve for s as follows:
r + s = 72
s + 8 + s = 72
2s = 72-8
2s = 64
s = 64/2
s = 32

Now, substitute with the s in equation I to get the value of r as follows:
r = s + 8
r = 32+8
r = 40

Based on the above calculations:
Robbin's number = r = 40
Sydney's number = s = 32

hope this helps :)

Answer 2

Robin’s number ------------ Y
Sydney’s number ------------ x

Y = X + 8.............. (1)

X + Y = 72 ............(2)

Substituting (1) in (2)
X + (X + 8) = 72 .............> ......2X = 64 => X = 32

Now in (1)

Y = (32) + 8 = 40

Robin is 40
Sydney is 32