Int. Algebra: Find r and t for 2r - t + 3 = 0, 2t + 3r = 15

Have you had NO introduction to simultaneous solution of equations? There wasn't a single example in your book or in your class? Not one?!

2r - t + 3 = 0
2t + 3r = 15

Solve one equation for one variable. It doesn't much matter which equation or which variable.

2r - t + 3 = 0
2r + 3 = t

Substitute this value into the other equation.

2t + 3r = 15
2r + 3 = t

2(2r + 3) + 3r = 15

Solve that for 'r'

You tell me how to find 't'.
 
Too bad you PMd me with your work.

I'll have to repeat it here for the benefit of others.

You solved well for 'r'.

2(2r + 3) + 3r = 15
4r + 6 + 3r = 15
7r + 6 = 15
7r = 9
r = 9/7

This is where you went somewhere funny. Don't convert things to decimal unless someone is forcing you to do so. Stick with the exact values.

Solving for 't', then:

2r + 3 = t
2(9/7) + 3 = t
18/7 + 21/7 = t
39/7 = t

Check these EXACT values in your ORIGINAL equations.
 
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