Answer:
311.6 cm
Step-by-step explanation:
To solve this problem, let's call:
k = Keith's height
n = nephew's height
Since the ratio is 15:7, we have
(1)
Then, Keith's height is increased by 16%, so the new height of Keith is
(2)
While the nephew's height is doubled:
(3)
We also know that Keith is now 34 cm taller than his nephew, so
(4)
Substituting (2) and (3) into (4), we get

And substituting (1),

Solving for n,

So the current height of the nephew is:

While Keith's current height is

So their total current height is

There are no sentences below about Roxy's claim
The slop is -1 and the y-intercept is (0,7) so then go on the graph and plot a point on the y- axis line at 7. Then go right 7 units and down 7 units and that should be it :)