Ask a question

if a+b=1000, and 7a+15b=11504, what is value of a and b?

solve for a and b


1 Answer by Expert Tutors

Tutors, sign in to answer this question.
Elina N. | Experienced Tutor Chemistry, Biology, Regents, SAT, CollegeExperienced Tutor Chemistry, Biology, Re...
5.0 5.0 (67 lesson ratings) (67)

First you have to solve for one of the variables in terms of the other.  Take one of the equations for example a+b=1000 and  solve for a to get a=1000-b.  Now you can substitute this expression into the other equation instead of a.  7a+15b=11504 becomes 7(1000-b)+15b=11504.   Now we expand the parenthesis 7000-7b+15b. Combine like terms 7000+8b=11504. Subtract 7000 from both sides 8b=4504.  Divide both sides by 8, b=563.  Now you can substitute b into either of the original expressions and solve for a.  It's best to use the easier one.  a+563=11504.  a=437.  Hope this helps.