Respuesta :

mac205

Step-by-step explanation:

let both unknowns be x and y

x = 5y. ......(1)

x + y = 90. ......(2)

sub eqn (1) into eqn (2)

5y + y = 90

6y = 90

y = 90/6

= 15

sub y = 15 to eqn (1)

x = 5y

x = 5 × 15

× = 75