Darla needs to purchase nine more stamps than envelops. each stamp cost $0.10, and each envelope costs $0.13 . if she pays $2.51, how many stamps and envelops does she buy.

This is a systems of equations.

s = stamp, e = envelope

Substitute e + 9 for s.

.1(e + 9) + .13e = 2.51

Simplify.

.1e + .9 + .13e = 2.51

Simplify.

.14e + .9 = 2.51

Subtract .9 from both sides.

.14e = 1.61

Divide both sides by .14.

e = 11.5

Now, you can input e into the other equation.

11.5 + 9 = s

Simplify.

20.5 = s

s = 20.5, e = 11.5

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°

the multiples of 15 are 15, 30,45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195,   210, 225, 240, 255, 270, 285, 300, 315, 330, 345, 360, 375,   390, 405, 420, 435, 450, 465, 480, 495, 510, 525, 540, 555, 570, 585, 600, 615, 630, 645, 660, 675, 690, 705, 720, and 735.

the factors of 15 are 1, 3, 5, and 15.

hope that , fam!

-une, your fren : )