Answer: Here are the answers. I walked you through 16 in my answer.
16. 3x=2y
1 =y-x
x=2 and y=3
17. $2.15=.10d+.05n
d=30-n
There are 17 nickels and 13 dimes
18. 18=4x+5y (since that's the total amount of holes and each par is either 4 or 5 strokes each)
4x=79-5y (since there are 79 total strokes and each was either 4 or 5)
No solution
Step-by-step explanation: For each problem, you have to write down the information you know, then define variables for the unknown. For 16, for example, they tell you that one number, which I have chosen to call x, is equal to two times the larger number, which I have chosen to name y. So, you'd have an equation that equals x. It also tells you that you need three times x, and two times y, which can be rewritten as 3x and 2y. In other words, 3x=2y. That said, you can move on to the next equation. Since you know the difference is 1, in other words, y-x=1, or y=x+1 ( I isolated y by adding x to both sides), you can put that into your equation as well. From there, I used the substitution method to solve.
3x=2y
so 3x=2(x+1)
y=x+1
3x=2(x+1) --- orig equation
3x=2x+2 --- distributive property (Multiplied x+1 by 2)
x=2 ---- subtracted 2x from both sides
**Now, to find y, you can substitute x into either equation. Since I know y=x+1 where x=2, I know that y must be 3. To check this, you can graph on Desmos. The lines should intersect at (2,3).
For 18, the lines are parallel so they never intersect. There is no solution.