I think of two numbers, which I represent by x and y. If I add three times to y to three times x, the result is 7 1/2, while if I subtract three times y from three times x the result is 22 1/2. What numbers do x and y represent?
3x + 3y = 7 1/2 - Equation 1
3x - 3y = 22 1/2 - Equation 2
= 6x = 30
= 6x/6 = 30/6
= x = 5
That’s about where I can solve it. Now I need help with the substituting part, on how to substitute x = 5 in Equation 1 or 2.
well, you have
3x + 3y = 15/2
or,
x + y = 5/2
If x=5, then
5 + y = 5/2
y = -5/2
I hope you can get away from mixed numbers soon. They are basically useless for real calculations.