Roberto is x years older than his only sister but 10 years ago he was twice her age. What are the current ages of the siblings?

S = x + 10

R = 2x + 10

Step-by-step explanation:

If R is Roberto's age, and S is his sister's age, then:

R = S + x

R − 10 = 2 (S − 10)

Solve with substitution.

S + x − 10 = 2 (S − 10)

S + x − 10 = 2S − 20

S = x + 10

R = 2x + 10

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