Well, the ratio of yellow beads to blue beads is 4:5. The best way I think is to guess and check multiplying the ratio by integers. You need between 15 and 20.
4 : 5 ( = 9 too little )
8 : 10 ( = 18 just right)
12 : 15 ( = 27 too much)
So per necklace, 8 yellow beads and 10 blue beads would be needed.
I hope this helps :-)
In this question, it is given that

Because of -5 inside the function, the graph shifts to 5 units right . If it was,

then, the graph shifts to 5 units down .
So out of the given four options, correct option is the last option that is option d .
The first one is 8 and here's a graph. the second one is 5 again here's a graph
The slope is 1/2
Anything in front of the x in slope-intercept form is the slope