If x is Maria's age, then Mario's age is x + 1.
The equation that represents the sum of their ages is x + x + 1 = 7.
By combining like terms, the equation becomes 2x = 6.
Hence, the value of x which represents the age of Maria is 6/2=<<6/2=3>>3.
So Mariu is 3 + 1 = <<3+1=4>>4 years old.
#### 4