Answer:
t=340 years
Explanation:
Let's call:
x=Height of The Matterhorn Glacier
y=Height of The Himalayan Glacier
The original value of x is 14,600 ft and it decreases at 10 ft per year, thus the function x is (t in years):
x=14,600-10t
Similarily the initial value of y is 18,000 and it decreases at 20 ft per year, thus the function is (t in years):
y=18,000-20t
Finding the value at which both heights are the same implies that x=y, therefore:
14,600-10t=18,000-20t
Joining variables to the left and numbers to the right:
20t-10t=18,000-14,600
Simplifying:
10t=3,400
t=3,400 / 10
t=340 years