At a dinner, Joe orders three strips of bacon and a cup of coffee and is charged $2.25. Stella orders two strips of bacon and a cup of coffee and is charged $1.70. What is the price of two strips of bacon?
I think you need more help than this site is designed for.
$3b+c = 2.25$ expresses that 3 pieces of bacon and a cup of coffee costs \$2.25
likewise $2b+c=1.70$ expresses that 2 pieces of bacon and a cup of coffee costs \$1.70
you can add and subtract equations to/from each other and still maintain them as equations
if you subtract the second equation from the first you get
$(3b-2b) + (c-c) = (2.25 - 1.70)$
$b = 0.55$
so the cost of 1 pieces of bacon is $0.55$
2 pieces of bacon will cost twice this or $2 \times 0.55 = \$1.10$
(cost of 3 pieces of bacon) + (cost of one cup of coffee) is (2 dollars and 25 cents)
translate to an equation ...
$3b + c = 2.25$
do the same process for Stella's order ...
$2b + c = 1.70$
solve using the method of elimination (have you heard of this method before?) ...
$\color{red}{3b} + \color{blue}{c} = \color{green}{2.25}$
$\color{red}{2b} + \color{blue}{c} = \color{green}{1.70}$
---------------- subtract each term from the one above it
$\color{red}{b} + \color{blue}{0} = \color{green}{0.55}$
this equation says one piece of bacon costs 55 cents ... so, how much would two pieces cost?
My point before was that the only difference between the two orders, "three strips of bacon and a cup of coffee" and "two strips of bacon and a cup of coffee" is one strip of bacon. The difference in the two costs, $2.25- 1.70= $0.55, is that one strip of bacon. Two strips of bacon cost 2(0.55)= $1.10.