−4x+7y=20 y=3x+15 cuanto vale y cuanto vale x
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Step-by-step explanation:
ANSWER
4x+7y=20⟶(i)
21x−13y=21⟶(ii)
Multiplying (i) by 21 and (ii) by 4.
84x+147y=420⟶(i)
84x−52y=84⟶(ii)
On substraction : 199y=336
y=
199
336
Putting the value of y⟶(i)
4x+7×
199
336
=20
⇒4x=20−7×
199
336
⇒4x=
199
3980−2352
∴x=
4×199
1628
x=
199
407
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