Question 1190343
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(1) I personally would never solve a pair of equations like this using substitution.  When the equations are both in this form ("Ax+By=C"), I would always use elimination.<br>
2x+3y=24
-3x-5y=15<br>
multiply the first equation by 3 and the second by 2 so that the x terms are 6x and -6x; then adding the two equations eliminates x.  You can then solve for y, and once you have y you can use either original equation to solve for x.<br>
6x+9y=72
-6x-10y=30
-y=102
y=-102<br>
2x+3(-102)=24
2x-306=24
2x=330
x=165<br>
ANSWER: x=165; y=-102<br>
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(2) Solving by substitution, you solve one equation for one variable in terms of the other and substitute that into the other equation.<br>
solve the first equation for x:
2x+3y=24
2x=-3y+24
x=-1.5y+12<br>
substitute that expression for x in the second equation:
-3(-1.5)y+12)-5y=15
4.5y-36-5y=15
-.5y=51
y=51/-.5=-102<br>
x=(-1.5)(-102)+12=153+12=165<br>
Same answer; but the work is a lot uglier....<br>