... numbers is 12 find the two numbers
Answers (1)
Given x/y = 1.75, x - y = 12
You have two lines. They look like this:
www.wolframalpha.com/input/?i=plot+x%2Fy+%3D+1.75,+x+-+y+%3D+12
Where they cross, approx x = 28 and y = 16, the values of x and y satisfy both equations simultaneously, so it is called a simultaneous system. There are two ways to find that point. Substitution is when you solve one equation for one variable and substitute that into the other equation.
x - y = 12
x = y + 12 Now put this in place of x in the other equation.
(y + 12)/y = 1.75 Multiply by y. This is called a "snake in the deal" because if you don't watch out you will get bit. Multiplying by a variable sometimes introduces false answers.
y + 12 = 1.75y Subtract y.
12 = 0.75y Divide by 0.75.
16 = y We lucked out this time, only one answer. Any time you multiply or divide by the variable, you have to check the answer in the original equation.
Elimination is when you add the equations in a way to eliminate one variable. Otherwise the process is the same. Elimination does not work well with this particular example. You try it and see what happens.
Check:
www.wolframalpha.com/input/?i=solve+x%2Fy+%3D+1.75,+x+-+y+%3D+12