math
posted by Jen .
Milan's gas tank is 1/5 full. After he buys 6 gallons of gas, it is 7/10 full. How many gallons can Milan's tank hold?

let x = number of gallons the when tank is full
according to first statement, initially the tank is 1/5 full. thus we can write it as (1/5)x
according to second statement, he bought 6 gallons, thus we add 6 to the initial amount, and it becomes 7/10 full or (7/10)x
rewriting using equations:
(1/5)x + 6 = (7/10)x
solving for x,, first we multiply both sides of the equation by 10 to get rid of denominators and deal with whole numbers:
10*(1/5)*x + 6*10 = 10*(7/10)*x
2x + 60 = 7x
60 = 5x
x = 12 gallons
hope this helps~ :)