Question 52264
To solve for a, you need to have {{{a}}} isolated on either the left or right side of the equals sign.  To do that in this case, divide both sides by {{{bx}}}, thusly: {{{c/(bx)=(abx)/(bx)}}}, which simplifies to {{{c/(bx)=a}}}.  For the second equation, expand it:  {{{-3*x+(-3)*(-5)=15}}}, which simplifies to {{{-3x+15=15}}}.  Now subtract both sides by 15 to get {{{-3x+15-15=15-15}}} which simplifies to {{{-3x=0}}}.  Dividing both sides by -3: {{{(-3x)/-3=0/-3}}}, which simplifies to {{{x=0}}}.