Two girder designs are under consideration for a bridge for a 1,200-foot crossing. The first design is expected to result in a superstructure weight per foot of 22(S) + 800, where S is the span between piers. The second design should result in superstructure weight per foot of 20(S) + 1,000. Piers and two required abutments are estimated to cost $220,000 each. Let X = the number of piers plus abutments. The superstructure will be erected at a cost of $0.55 per pound. Choose the girder design that will result in a minimum cost and specify the optimum value for X. Hint: X must be an integer.

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

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step-by-step explanation:

all you have to do is multiply them both to see how many out comes you can put:

3 x 2 = 6

you can make 6 diferent combinations of crusts and toppings.

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