5x + 10y = 18
x = y - 6
which of the following equations is the result of substituting y - 6 in for x in the first equation?

5x + 10y - 6 = 18
5y - 6 + 10y = 18
5y - 30 + 10y = 18

Ageologist had two rocks on a scale that weighed 4.6 kilograms together.rock a was 0.5 of the total weight.how much did rock a weigh?

I'm confused on this could anyone me and show me what i need to do to solve it.

Atruck can be rented from company a $50 a day plus $0.60 per mile. company b charges $20 a day plus $0.80 per mile to rent the same truck. find the number of miles in a day at which the rental costs for company a and company b are the same