Question 1012058

In 1950 Roberto was four times as old as Juan. In 1955 Roberto was three times as old as Juan. How old was Roberto when Juan was born?
<pre>Let Juan’s age, in 1950 be J
Then Roberto’s age, in 1950 was 4J
Therefore, difference in ages = 4J – J, or 3J
In 1955, Juan was J + 5, and Roberto was: 4J + 5
We then get: 4J + 5 = 3(J + 5)
4J + 5 = 3J + 15
4J – 3J = 15 – 5
J, or Juan’s age, in 1950, was: 10
Roberto’s age, in 1940, when Juan was born, was 3(10), or {{{highlight_green(30)}}}