Which value if x makes this proportional true? 14/20=56/x A. x=62 B. x=70 C. x=80 D. x=100

Work Shown:

Let's cross multiply to get the following

14/20 = 56/x

14*x = 20*56

14x = 1120

x = 1120/14

x = 80

As a way to check the answer, we can type 14/20 - 56/80 into the calculator and we should get 0. I'm taking advantage of the rule that if A = B, then A-B = 0. This trick is handy to check if two sides of any equation are equal to one another.

(0,-3) see attached graph

step-by-step explanation:

a. to solve the system, graph the two equations.

x = y+3 becomes y=x-3 has m=1/1 and b=-3. start at (0,-3) on the y-axis and plot a point. then move up 1 unit and 1 unit to the right. plot a point and connect.

y=-4x+3 has m =-4/1 and b=-3. start at (0,-3) on the y-axis and plot a point. then move down four units and to the right 1 unit. plot a point and connect.

the solution is the point (x,y) where the two lines intersect. by the graph below it is (0,-3).

b. to solve by substitution, substitute y = -4x-3 into x= y+3

x= (-4x-3) +3

x=-4x

5x=0

x=0

now substitute x = 0 back in to find y.

y= -4(0)-3

y=0-3

y=-3

solution is (0,-3)

c. use elimination by adding the equations together.

x-y=3

4x+y=-3

5x=0

x=0

then substitute into one equation to find y.

y=-4(0)-3

y=-3