Mr. robinson write a novel and a book store on sale for 20% off its regular price of $29.99. mr. chang brought the same novel at a different bookstore for 10% off its regular price of $25.which person received the better discount

Mr. Chang got the better deal.

Step-by-step explanation:

Robertson: He paid 100% - 20% = 80% of the cost of the book.

80% * 29.99 = 80/100 * 29.99 = 2399.2/100  = 23.992

Chang: He paid 10% off $25.00

10% of $25.00 =  2.50 dollars. I'll let you go through the steps to get this.

With the  discount, Mr. Chang paid 25.00 - 2.50 = 22.50

Conclusion

Mr. Chang got the better deal by $1.49

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