If a:b=4:7, find the following(iii) \left( 5a-4b \right)/\left( 2a-3b \right)
If a:b=4:7, find the following(iii) \left( 5a-4b \right)/\left( 2a-3b \right)

The ratio is used for comparing two quantities of the sane kind.

The ratio formula for two numbers says a and b is given by a:b or a/b. When two or more such ratios are equal, they are said to be in proportion.

The concept of ratio and proportion is majorly based on ratios and fractions.  

Solution:

From the question it is given that,

a:b=4:7

a/b=4/7

\left( 5a-4b \right)/\left( 2a-3b \right)

Now, divide both numerator and denominator by 'b' we get,

=\left[ \left( 5a/b \right)-\left( 4b/b \right) \right]/\left[ \left( 2a/b \right)-\left( 3b/b \right) \right]

=\left[ \left( 5a/b \right)-4 \right]/\left[ \left( 2a/b \right)-3 \right]

Now, substitute the value of a and b we get,

\left[ \left( 5\left( 4/7 \right) \right)-4 \right]/\left[ \left( 2\left( 4/7 \right) \right)-3 \right]

=\left( \left( 20/7 \right)-4 \right)/\left( \left( 8/7 \right)-3 \right)

=-8/-13

=8/13