Consider the system {12x+3y=40 7x-4y=38a. explain how you know there is a unique solution to this system. b. explain how you can tell that the point (2.5, -3.4) is not a solution to the system.

The two linear equations in two variable is:

12 x + 3 y = 40

7 x - 4 y = 38

(a) For a system of equations in two Variable

a x + by = c

p x + q y = r

It will have unique solution , when

As, you can see  that in the two equation Provided above

So, we can say the system of equation given here has unique solution.

(b). If point (2.5, -3.4) satisfies both the equations, then it will be solution of the system of equation, otherwise not.

1. 12 x+3 y=40

2. 7 x-4 y=38

Substituting , x= 2.5 , and y= -3.4 in equation (1) and (2),

L.H.S of Equation (1)= 1 2 × 2.5 + 3 × (-3.4)

                             = 30 -10.20

                               = 19.80≠ R.H.S that is 40.

Similarly, L H S of equation (2)= 7 × (2.5) - 4 × (-3.4)

                                                  = 17.5 +13.6

                                                  = 31.1≠R HS that is 38

So, you can Write with 100 % confidence that point (2.5, -3.4) is not a solution of  this system of the equation.

answer: 7 x 2/5 = 2.8 hours, is your answer. your welcome! : 3

step-by-step explanation: first work out how long it took to hose 1/7 of the lawn which is 2/5 hours. times that by 7 to get the whole lawn.

sorry i don't know the other answer. i didn't learn what a proportional relationship is.