How do you solve 4x plus 3y equals 90?

Answer 1

We have two unknown and only one known.

This mean that we need to set a fixed value to one unknown and we can calculate the other.

Example:

4x+3y=90

we say that X = 15

then the question is:

4*15+3y=90

We simplify:

3y=90-4*15

3y=90-60

3y=30

We divide by 3 on both sides of equal.

y=10

By this we know that if x=15 then y must be 10 for the result to be 90.

When dealing with 2 unknown we normally use the X and Y values in order to draw a graph.