Question

Calculați 3 x a + 7 x b Știind ca ( 104 x 4 + 83 x 5 ) - a x 3 = 4 x 1809 : 9 și ( 9 x 7 + b - 5 x 8 ) - 5 x 5 + 70 = 75

Answer 1

(104×4+83×5)-3a=4×1809:9 ⇒416+415-3a=804⇒-3a=804-831⇒-3a=-27⇒a=9
63+b+40-25+70=75⇒148+b=75⇒b=-73
3a+7b⇒3×9+7×(-73)=27-511=-484

Answer 2

( 104 x 4 + 83 x 5 ) - a x 3 = 4 x 1809 : 9 
416+415-ax3=4x201
831-ax3=804
ax3=831-804
ax3=27
a=27:3
a=9

( 9 x 7 + b - 5 x 8 ) - 5 x 5 + 70 = 75
(63+b-40)-25=75-70
(63+b-40)-25=5
(63+b-40)=5+25
63+b-40=30
63+b=30+40
63+b=70
b=70-63
b=7

3xa+7xb=3x9+7x7=27+49=76