Which of these systems of linear equations has an infinite number of solutions?

a. 3x-8y=21
6x-16y=46

b. 3x+6y=22
6x+12y=44

c. 5x+9y=2-
10x-14y=48

d. 5x-9y=20
10x+18y=40

Use the distributive law to multiply. 3(4x + 5y + 6)

If sr is 4.5cm and tr is 3cm, what is the measure in degrees of angle s?

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?