Question 1135159
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With algebra, define a variable and write an equation using that variable and the information given in the problem, then solve the equation.<br>
Often, especially for students just learning algebra, the best choice for the variable is the number the question asks for.<br>
In this problem, you are to find Mario's current age.  So<br>
let x = Mario's age now<br>
Use that variable and the given information to find expressions for the other numbers in the problem -- Kris's current age, and both of their ages 3 years from now.<br>
then x-4 = Kris's current age
x+3 = Mario's age 3 years from now
(x-4)+3 = x-1 = Kris's age 3 years from now<br>
Now write and solve the equation that says Kris's age 3 years from now will be 2/3 of Mario's age then:<br>
{{{x-1 = (2/3)(x+3)}}}<br>
The easiest first step for most students is to multiply by 3 to get rid of the fractions....<br>
{{{3(x-1) = 2(x+3)}}}<br>
After that it is basic algebra to the answer.  I will assume you know enough basic algebra to finish from there.<br>
But the important part of the problem for a beginning algebra student is to understand how to get from the statement of the problem to an equation that can be solved.<br>
I always try to encourage students to think about how the problem could be solved without the formal algebra -- it's good brain exercise.<br>
Here is how you might do that.<br>
(1) The difference in their ages is 4 years.
(2) When Kris is 2/3 of Mario's age, the difference in their ages will be 1/3 of Mario's age. (Mario's age, minus 2/3 of Mario's age, equals 1/3 of Mario's age)
(3) So the 4 year difference in their ages will be 1/3 of Mario's age when Mario is 4*3=12.
(4) It is in 3 years from now that Kris will be 2/3 of Mario's age; since that will be when Mario is 12, Mario is now 9.<br>
CHECK:
Mario is 9, so Kris is 9-4=5.
In 3 years, Mario will be 12 and Kris will be 8 -- and 8 is 2/3 of 12