Sagot :
Sally is older because:
Sally:6
Thomas:3
Twice Thomas's age is 6.
6+6=12
Equation:6+3x2 or (6+3)x2 hint:PEMDAS
Solved:12
s=sally
tomas=t
s+2t=12
s-t=3
add t to both sides
s=3+t
subtitute 3+t for s in first equation
3+t+2t=12
3+3t=12
subtract 3
3t=9
divide by 3
t=3
tomas=3
subsitute
s=t+3
s=3+3
s=6
sally=6
tomas=3
tomas=t
s+2t=12
s-t=3
add t to both sides
s=3+t
subtitute 3+t for s in first equation
3+t+2t=12
3+3t=12
subtract 3
3t=9
divide by 3
t=3
tomas=3
subsitute
s=t+3
s=3+3
s=6
sally=6
tomas=3