Can some one refresh my memory on how to do this

11.

3x - 2y = 2

5x - 5y = 10

We can divide the second one by 5,

x - y = 2

and multiply by 2,

2x - 2y = 4

Subtracting from the first equation,

3x - 2y - (2x - 2y) = 2 - 4

x = -2

y = x - 2 = -4

Check:

3x - 2y = 3(-2) - 2(-4) = -6 + 8 = 2 good

5x - 5y = 5(-2) - 5(-4) = -10 + 20 = 10 good

x=-2, y=-4

12. Factor

First we take out the common factor of 2. Then we need two numbers that add to 11 and multiply to 30; that's 5 and 6.

2(k+5)(k+6)

13.

5x+3y = -15 Solve for x given y=0

5x+3(0)=-15

5x = -15

x = -15/5 = -3

-3

step-by-step explanation: so we look at the formula un = a + (n-1)d

un is the amount of seats

n is the nth term aka row number

a is the original sequence/row number

d is the difference between each term

so in this a=22 d=6 and n can remain as n because we are simply formjng a rule

lets put these in the equation

un=22+(n-1)(6)

this is your answer to part a

however

lets double check that this is correct, we'll try putting it into the second term

un=a+(n-1)d

u2=22+(2-1)(6)

u2=22+6

u2=28

as the question said the second row has 28 seats so now we know the formula we made is correct.

as for part b

un=a+(n-1)

its asking us to find a row with 100 seats.

remember un was the amount of seata so all we do is substitute this in.

un=100 a=22 d=6

un=a+(n-1)d

100=22+(n-1)(6)

so now we simplify to find n which is the row number.

100-22=22+(n-1)(6)-22

78=(n-1)(6)

78/6=(n-1)(6)/6

13=n-1

13+1=n-1+1

14=n

so now we know that in the 14th row there is 100 seats.

hope this and that you understood! its my first time using the app or anyone out on here : p its also me to revise so a bunch! ask more questions if you dont understand ☺

70 years.

step-by-step explanation: