You put 4 in the X
1/2(4)+5y-10<0
2+5y-10<0
-8+5y<0
5Y<8
Y<8/5
The answer is 5.83
Use the Pythagorean Theorem to calculate the 3rd side length.
a^2+b^2=c^2
3^2+5^2=c^2
Let x gallons be the amount of pure antifreeze that should be added to the 30% solution to produce a solution that is 65% antifreeze. Then the total amount of antifreeze solution will be x+3 gallons.
There are 30% of pure antifreeze in 3 gallons of solution, then
3 gallons - 100%,
a gallons - 30%,
where a gallons is the amount of pure antifreeze in given solution.
Mathematically,

Now in new solution there will be x+0.9 gallons of pure antefreeze.
x+3 gallons - 100%,
x+0.9 - 65%
or

Answer: he should add 3 gallons of pure antifreeze.
3pie+12mm is the correct answer (A)