When solving the system x + 2y = 9 and x - y = 6 by substitution, what can be substituted for x in the second equation?

X+2y = 9 eq.1
x-y =6 eq.2

x = 9 -2y (from eq. 1)

Now substitute the value of x in the second eq.2

9-2y-y =6
-3y = -3
y =1

So,
x +2 (1)= 9
x= 7

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.