Two friends went to a restaurant and ordered one plain pizza and two sodas . their bill totaled $15.95. later that day, five friends went to the same restaurant. they ordered three plain pizzas and each person had one soda. their bill totaled $45.90. what's the system of equations to determine the price of one plain pizza

The system of equations you'll need is:
P+2S= 15.95
3P+5S= 45.90
P= Plain pizza and S=sodas
We can also solve using elimination. By just multiplying the first equation by -3 to eliminate p.
-3p-6s=-47.85
3p+5S=45.90
(-S=- 1.95)/-1
So, one soda is 1.95. Let's put S value in the first equation.
P+2(1.95)= 15.95
P+3.90= 15.95
15.95-3.90
12.05
A plain pizza is equal to 12.05. Let's check our values by using the second equation.
3(12.05)+5(1.95)=45.90
36.15+9.75=45.90
45.90=45.90
So, the price of a plain pizza is $12.05.