Solve the sytem below using elimination
2x - 4y = 10
X + 5y = 40

Add -2 (second equation) to the first equation to eliminate x :

(2x - 4y) + (-2) (x + 5y) = 10 + (-2) • 40

(2x - 4y) + (-2x - 10y) = 10 - 80

-14y = -70

y = 5

Plug this into either equation (I'll use the second) to solve for x :

x + 5y = 40

x + 5 • 5 = 40

x + 25 = 40

x = 15

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)