The sum of three numbers is 72
The second number is 7 times the first.
The third number is 18 less than the second
What is the first number?

Let the first number be x, second number be 7x and the third number be      7x-18. Then,

Sum of the numbers=72

or, x+(7x) +(7x-18)=72

or, 15x=90

or, x=6

So, the first number is 6.

7 weeks

step-by-step explanation:

convert each fraction to the least common multiple of 20, so 3/4 = 15/20 & 1/10 = 2/20, then divide 15 by 2 and you get a little over 7, so the food will last 7 weeks.

2.2°  

step-by-step explanation:

let θ = the angle of elevation.

tanθ =77/2020

tanθ = 0.038 12

      θ = tan⁻¹0.038 12

      θ = 2.2°