How do you solve 2x=y-10 in substitution

Y=x+1
2x+y=10 

all you do is add part A into Part B , meaning plug it in and solve like a regular equation. 
2x + x + 1 = 10 
3x + 1 = 10 <--- one one from one and ten 
3x = 9 <--- divide 3 from both sides 
 

2(3)+y=10 
6 + y = 10 <-- minus 6 from both sides 
 
plug it in to check.! 
2(3) + 4 = 10 
6 + 4 = 10 
10 = 10. hope that helped

Num of plants = (original#ofplants)*(1.6)^t

Think of it as five or above give it a shove. change the 5 or above to the right to a zero and add one to the number on the left.