Question

in triangle abc angle a + angle b =65° and angle b + angle c=140° . find the value
angle a​

Answer 1

$∠A+∠B=65o−−−(1)$

$∠A+∠C=140o−−−(2)$

we know ∠A+∠B+∠C=180o

from (1)65o+∠C=180o from (2)

$∠C=115o$

from $(2)$

$∠A+∠C=140$

$∠A+25=65o$

$∠A=40o$

$from (1)∠A+∠B=65o$

$∠B=25o$