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a. 2

b. 2(9+5) = 28

Step-by-step explanation:

18 = 3 × 3 × 2

or (3 power 2 × 2)

10=2×5

a . GCF = 2

b. factor out 2 out of both 10 and 18 which their sum is 28 and write every thing that is left in the prantheses .

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°

ratio is 2 : 9

the answer is three

13.5 : 3