Question

210:[(15xa-30):3-15] =7​

Answer 1

Răspuns:  a = 11

Explicație pas cu pas:

210 : [( 15 x a - 30) : 3 - 15] =7​

( 15 x a - 30) : 3 - 15 = 210 : 7

( 15 x a - 30) : 3 - 15 = 30

( 15 x a - 30) : 3 = 30 + 15

( 15 x a - 30) : 3 = 45

15 x a - 30 = 45 × 3

15 x a - 30 = 135

15 × a = 135 + 30

15 × a = 165

a = 165 : 15

a = 11 → numărul, aflat prin metoda mersului invers

Verific:

210:[(15x11-30):3-15] = 7

= 210 : [(165-30):3-15] =

= 210 : ( 135 : 3 - 15) =

= 210 : (45 - 15) =

= 210 : 30 =

= 7

Answer 2

$\it 210:[(15\cdot a-30):3-15]=7 \Rightarrow (15\cdot a-30):3-15=210:7 \Rightarrow\\ \\ \Rightarrow (15\cdot a-30):3-15=30|_{+15} \Rightarrow (15\cdot a-30):3=45|_{\cdot3} \Rightarrow \\ \\ \Rightarrow 15\cdot a-30=135|_{+30} \Rightarrow 15\cdot a=165|_{:15} \Rightarrow a=11$