Given a+b=7 and a-b=3, find: 3a:3b

Answer & Step-by-step explanation:

We are given two equations ...

a + b = 7

a - b = 3

We are asked to find 3a : 3b. In order to find the value of a and b, we have to rearrange one of the equations so it will be easier to find the values of the variables. Let's rearrange the second equation.

a - b = 3 → a = 3 + b

Now that we have an equation that shows the value of a, we can use this equation and plug it into the first equation.

a + b = 7

a = 3 + b

(3 + b) + b = 7

3 + 2b = 7

2b = 4

b = 2

We have the value of b. Now, we have to find the value of a by plugging b into the second equation.

a - b = 3

b = 2

a - 2 = 3

a = 5

Now that we have the values of both variables, we can plug them into (3a:3b)

3a : 3b

3 (5) : 3 (2)

15 : 6

5/2 or 2.5

So, 3a : 3b equals 5/2 or 2.5